Peter Beeney

    Timbo,   Thanks also for your comments. But as with Brian, I would consider all this applies equally as well to 35MHz. I hope I was not trying to question the operator, just the low voltage situation.     Taking your last example, the 4 cell pack at 4 volts open circuit. I would more than agree that this is so flat it would slide under a snake's belly! With a top hat on! But, I would also say that a reset is also pretty useless as well, as soon as it operates and resets, it will trip out again.     When my senior friend is back from his hols I will experiment with his kit, if the AR500 has this brown out facility I will tamper with it somewhat. Then I'll try and discover what happens when I also poke that big red switch. Knowing my luck, nothing!     Think I'll go and switch the landing lights on.                             PB     

    Brian,  Thanks for your comments.    Yes, a valid point. However, I think these type of faults may result in a 'black out', a total loss of power. They would also affect 35MHz, too. I have to say, in many years of bashing beginners models I have always been surprised at the lack of trouble caused by these ancillary items. They always seem very tough and resilient, despite some of the treatment that's handed out.     This 'test bed' was an i/c model, and of course did not have a voltage regulator. Voltage regulators I'm quite happy to discuss, but they are an entirely separate entity. The considerations are completely different.     My personal view is that if I considered that the power supply was reaching these low levels, however momentarily, I would beef it up until it didn't. And I'm satisfied, for all the reasons above, that a normal model, with a sound battery, in a good state of charge, does not allow the supply voltage, at the receiver, to indeed drop to this level.        Now I feel a bit flat, think I'd better recharge a little!                   PB     

    John,     I've now learned that the receiver that my friend was using when he had the first failure was an AR500. As is the replacement also. He's on holiday at the moment, but when he returns I think he will be still slightly apprehensive.     This whole concept of the brown out intrigues me, so as promised I've had a little fiddle with it. If my understanding is correct, if the receiver voltage falls to 3.5 volts the receiver shuts down and has to reset. This is fine, but what I can't understand is why, or perhaps how, the rx voltage should fall to this level in the first place. So I've done some experiments. I do have some figures, which were very much in inline with what I expected. The tests were pretty basic, but I think sufficient. As before, using a hack model, with the battery in an unknown state of charge, to simulate normal conditions.     I previously stated that constantly moving the servos gave a 206 milli-volts drop. Trying to reproduce Phil's 'two bags of sugar' idea on the elevator, I half operated the elevator, to get maximum purchase, and then by grasping the surface and trying to return it to the normal position, as hard as I could, the servo was really buzzing, resulted in a 167 milli-volts drop. Multiplying this by 4, and as it's difficult to see that there is ever much load on the throttle servo, so would 3.5 be better, would yield a 656 milli-volts drop. Then I locked two servos, so that they were unable to move, and operated the two controls together, 359 milli-volts drop. So if all four servos were stalled together you could expect a 718 milli-volts drop. Then I tried an artificially heavy load, but this really is speculation because it's very difficult for me to see how this could happen under normal conditions. Because I was discharging through the switch harness etc. the discharge unit would only let me discharge at a max of 2.56A. At this discharge rate the battery took 8.5 minutes to reach 3.5v.     To get an instantaneous drop to 3.5v I think you would need to attempt to discharge at perhaps many hundreds of times C, which is somewhat impracticable, because at around 70 - 80 amps the battery wire insulation suddenly becomes liquid and drips off, sometimes alight, and the wire glows incandescent before burning through. I've done this trick, too!       This was a perfectly standard model, Sanwa servos, Futaba 35MHz 128 DF rx. 700mAh hydride battery. As before, all the voltage reading were at the receiver. The quiescent, or idle, current was 35 milli-amps. The quiescent voltage was around the 5+v mark. Thus there weren't any of the 'stalled servo' type tests that got down anywhere near down to 3.5v.     I think if I substituted a 2.4 rx here and then someone later told me I was suffering from delayed action brown outs I think I would be tempted to also look for other reasons for the problems!     Hope this is of interest.                                  PB

Yes, re the tx/rx question, I was trying to establish which one is at fault. I'd settle for the rx to start with.     Re. the brown out. If this lower limit is 3.5v then I find it rather incredulous that these sort of levels can be reached, even momentarily. I've just had a little play with a model. An aeroplane, that is. Seagull 40, oldish but sound 4 cell hydride pack. Not been charged since I flew it on Wednesday. The 'system idle' voltage = 5.191v. Stirring all the sticks constantly for one minute, that's rudder, elevator and throttle servos working constantly, the lowest reading I got at the end was 4.985v, a difference of 206 milli-volts. Using just the elevator, as you would when flying, then system idle = 5.189v, after one minute the lowest reading was 5.129v, a difference of 60 milli-volts. All voltages at the receiver. This test was not the most accurate, but got enough for a  quick check. Certainly I would not expect this level of effort in the air. So how do we frequently get down to the low voltage levels at the receiver? Could the brown out be something of a red herring? I do not know, but I will try and find out exactly what it takes to get down to 3.5 volts.     All interesting stuff, carry on the good work.                      PB    

    John,   I will try and get some info on the rx but the man is on his way to Cornwall at the moment. But I'm sure someone else might well know.     Timbo,  The model went into 'failsafe' mode, most likely a loss of signal. But that points to the 'sent' signal, the tx. If it were the rx at fault, that would be the 'received' signal. And the common factor in all this does seem to be the receiver..     I'm not entirely sure what a 'brownout' is exactly, I've not studied this, but when I played about with low voltage checks on 35 gear some years ago I found some interesting facts. When I applied a steady voltage of 4 volts and below the servo centres would start to change. Also the servos became very slow to operate. So it's my guess that at 3.5 volts all the control surfaces have stepped to one end and are not moving anyway. Or, at least, only very slowly.  So it's perhaps difficult to see how control can be maintained at this level, even if the rx is still working.  Interestingly, the 35 rx itself would still work well at 3.85 volts but stopped dead at 3.8 volts.     As you say, there could be a number of reasons why this happened but it was thoroughly checked out before flying. It could also be an inherent problem in the system. As an outside observer to all of this, I'm slightly surprised that Spektrum accept returned radios with such consummate ease. And then they all seem to return to sender with the same standard letter.     Maybe this is a situation that will lurk around for a while.  We have yet another new pilot about to begin, using a Spektrum. I shall now follow his progress with some enthusiasm.....                             Incidentally, I believe there was at least one possible sort of explanation for the Marie Celeste.                                         PB  

     I wonder if I might add a line here because as it so happens, we have also recently had an occurrence of a similar nature involving Spektrum radio.     Very recently a new learner pilot purchased a Spektrum radio, would this be a Spektrum 5E?, I'm not absolutely sure on that, and he installed it in a Boomerang which he'd recently repaired, broken due to pilot error, (his), when flying using a 35 set.  An experienced pilot, who does use 2.4, Futaba, carefully checked it all out and gave it a test fly. After taking off, it circled ok for about 3 - 5 minutes when suddenly all control was lost, with the engine shutting down. The model was at height, but began to descend. He was able to demonstrate, by moving the sticks, that he had no control. Fortunately, just before impact, control was restored and he was able to land. The owner instantly changed the radio at the model shop for another one.     On Wednesday I flew the new set-up using the same battery, etc. as was used before. On the first flight, the motor, a SC 46, cut at around 7 minutes, this was just a motor problem, but after a couple of small adjustments we were soon doing full 15 minute flights. We continued all the afternoon, from around 2 until 7, so the radio was on for at least 2 - 3 hours, perhaps longer. It did not miss a beat.  As my new pilot remarked, he'd probably more than doubled his total flying time in one hit!  And his trust in Spektrum was largely restored.        Apart from being involved in some serious 2.4 interference, related in another thread, 'Interference on 2.4 GHz?',  I've had very little 2.4 experience. However, I have done volts-drop tests on electrical equipment, and also some on model radio, mostly on things such as battery-backers etc. where I think there may well be a problem. Using a standard 4 servo radio set-up, and a battery in a reasonable condition, and in a good state of charge, I would need a great deal of convincing that there are any serious voltage excursions, certainly in the order of 1 volt, between the battery and the receiver.     The battery voltage, using a typical 4 cell pack will be about 5+ volts, and the volts drop, when 1 servo is activated, across the switch harness and battery wiring, will be in the order of milli-volts, not volts. I would say that servos generally operate more or less one at the time, in fixed-wing trainer type aircraft, not a really heavy load.     I don't know what caused this malfunction, I think I would call it a 'loss of control,' but it certainly happened. Also some other Spektrum equipment in our club, in fact all of it, has been replaced because of similar problems. The replacements, I believe, have been completely trouble free.                Not sure if this narrative is of any use, but it adds slightly to the total. Hopefully, the problems will soon be resolved.                 PB

     Derek  -  Pleased that I was able to be of assistance!  -  Your power supply chain is in the right order, I thought it must be!  -  The expo. You're right, always use the instructions. I accept full responsibility for what I do, it's just that I throw everthing in to start with, after that it only gets easier. I'm with you on the rates, in the 30 odd years they've been around I think they've probably caused more problems than they've cured.  -  The AR3900. Sorry, I'm Multiplex, and I'm waiting for their 2.4 GHz. There must be plenty of people with the info. you want though.                           Very Best Wishes.              PB           David  -    Very sorry for all the hassle caused.   It says here, Powerful Word Processor, I just didn't realise how powerful. Won't it be nice when eventually one computer program will actually be compatable with another one.       Anyway, I've finished for now, must get some flying in while this fine weather is on.                      Cheers.                                  Pete.  

      Derek,    I might have semi-cracked this problem.    I’ve pulled the text outside the thread, so I’m now able to read your post. I hope you will be able to read this reply.         The term redundant simply means ‘surplus to requirements.’ However, in engineering circles it’s sometimes just slightly different. If I had a battery say, supplying some equipment that could not be switched off under any circumstances, then I might arrange for a second battery that I could connect in parallel, without interruption, seamlessly in today’s jargon, a no-break change over in my old fashioned speak, so that I can take the first one out of service for maintenance purposes etc. This second pile of amps would be my redundant battery. In your case the two parallel supplies are there only in case one fails. They are always connected. It’s just a duplication.  One is redundant. ‘Belt and braces,’ so to speak The first you would know about a failure is if it happened when you’d forgotten to switch one on!     Going back to what I said about the series/parallel combo and the balancer ‘seeing’ only two cells, consider it this way. You are actually ‘looking at’ four cells but you are only ‘seeing’ two cells. If the pack were sealed in a black plastic bag you would ‘know’ there were only two cells, simply because it’s a 7.4v output.     So now you’re ahead of me and you can tell me that whether you switch one or both switches you are only ever connecting ‘two’ cells, that’s a max of 8.4v fully charged, to the regulator.     Is your power supply system in the order - battery - regulator - switches - receiver? Or battery - switches - regulator - receiver? It might be worth just considering this.     I can well believe the awesome model, a lot of practise to get up to top whack! Still, if you ever get to a full throttle flight at 3 kW, then it’s only going to fly for about four and a half minutes, something of a relief, perhaps?     The propeller, I can only say try someone like West London Models. There must be a demand, so there’s surely a supplier.     Re the exponential, I’ve got a sort of ‘less is best’ mentality. I would tend to start with none and then put in small amounts if necessary until I felt comfortable with it.     And the Ultra Duo 50. I don’t know this baby, I’ve used a Schulze for many years. However, I certainly agree with the maxim of a serious charger for serious charging. Plus they don’t get much better than Graupner. The improvement is just a measure of the quality, (or lack of it), of your previous battery basher perhaps. Over time, I’m sure it will prove to be a good investment, for too many reasons to go into here.     Good Luck with your model.                       PB    

    Derek,        I will try and answer your post, but at the moment the ads are appearing on top of the text in this tread, and so I can’t read what you’ve written. It happens in Safari 3, Firefox and Opera browsers so I guess it’s a problem for the system administrators. I could attempt a stab at an answer, but I’d prefer to wait. I’d be guessing.     Hope you can read this reply ok!        PB

     Soeren, thanks for that.     It does seem, as it stands, there are some tiny questions here. This only my personal view, but regarding the batteries I would consider that most importantly it’s not a good idea to run the cables close together over distance. You may possibly be able to cross the wires over ok. But separating them entirely must be best.     I shall have to try and have a little think about the lead from the Hall device. I’d have thought that this is only a trigger circuit and as such would only be a very small current. Quite why it has such a big effect is surprising. If it’s the actual capacitor discharge and then then the subsequent high voltage spark that doing the damage why does shielding the lead make a difference? Or is it in fact just acting like a little aerial, somehow radiating high voltage spikes? I’m intrigued, and I’ll have to do a bit of digging to see if I can reach some sort of answer. We’ve a few petrol engined models in the club, I shall do a few autopsies, and probably succeed in making myself even more confused. Incidentally, if it’s comparatively easy to operate the device without turning the engine, I suspect this will generate a spark just by turning it pass the trigger point, so maybe you can make some sort of a preliminary test without running the engine.     I think it would be interesting if you can establish what sort of interference this is. If it’s power line spikes then it would point to the fact that 2.4 is open to this, we’ve both experienced the effects. If, however, it’s r.f. then that would appear to contradict, if only in a minor way, the convention that 2.4 cannot be interfered with. Your ‘Faraday Cage’ would appear to be blocking some sort of emissions, and Brian’s suggestion about a fault on the 0 volts line must be worth a real good look. But, if if there were a HR, High Resistance, point, say, in here somewhere, would the motor run satisfactorily? I’m convinced that the power involved here is very low….       It well may be worth your while to see if you can prove the reason for your problem.     Certainly your 35 MHz experiences seem to bear out what I thought I’d seen in the past. 35 doesn’t seem prone to power problems. The HT lead was inevitably the sticking point here!     This is a long shot, but do the battery leads to the rx run anywhere near the sensor lead?     If you are prepared to experiment a little bit, you could try removing the foil screening, test the model to make sure the interference has returned, and then wrap the rx battery, leads where possible, and rx in foil, bond it all to to the engine bearer, because that’s at 0 volts, neg ignition battery, and see if that effects any sort of cure. This is very much poke and hope stuff, but if you should try it, and you get a result, then that might conclusively prove that the interference is on the power supply. The fact that it’s happened to these different makes of receivers suggests that it’s a common fault.     It does seem odd, though, that no one else has suffered this type of problem. I’d have thought that at least someone, somewhere, would have experienced glitching servos. At least once.        I have to say, I think I’ve now concluded what everyone else has probably long known, that any radio frequency ‘interference’ will not be able to affect the servos. So by default all these problems must be power supply based.         Good Luck.                      PB     Another thought. At our suggestion, my friend installed his battery very close to the engine. And the sense lead…… I’m now waiting for the call to say he’s crashed and it’s all my fault…       All very odd indeed!

    Brian,  thanks for your reply.     I think we’ve cured the problem simply by separating the batteries. And, more importantly, the cables. I’m convinced mutual inductance was the bogey.  Undoubtedly there are still spikes on the ignition battery supply cables but as there is now space between them and the rx supply they can’t do any harm. Maybe, and this is only Maybe, a tiny part of the problem is that 2.4 receivers are susceptible to transients on the power supply. Or it might have been this one rx.     I would say the CDI’s internal decoupling, or smoothing, is minimal, and even if we could get a spec, which I doubt, it would probably be written in Chinese.     There’s a 99% chance the the ign battery was a hydride. I didn’t take that much notice at the time. However, I suspect that in general the battery must be in good nick otherwise he would soon be bending my ear. This pilot is not an electrical man. Thus the internal impedance must be at least not higher than normal. I’d say the average discharge is also normal, it’s just that the current seems to flow in very sharp pulses.  But I did particularly notice the rx pack.     The basic answer to the rest of your questions is, in a word, no. Or, unknown. However, when I spoke about the ‘complete integrity’ I meant doing all those things to start with, to eliminate any problems as you are suggesting.     My ‘spot of tinkering about with’ really means exactly as you are suggesting, a test bed, with some test instruments to try and find out at least something as to what is going on. But this all take time and effort, and at the end of the day, who, apart from thee and me, is going to really be interested? These days, the only experiments I do are those that relate directly to my flying.     With regard to 35 MHz, I have a colleague, only one, we go back a long way, and for many years he built and flew large models, up to quarter scale. All with petrol engines. He was an electrical man and as far as I know he was never fussy where he put the batteries. He would have used them as G of G adjustments, perhaps even strapped together. He used JR PCM, and I watched him fly a great deal. He never had a moments bother with power supplies.       Just for interest, I spent my working life fighting volt drop. I occasionally do a few checks on some equipment and the results can be surprising. When management talks about ‘boys and toys’ she really has no idea how accurate the ‘toys’ description seriously is!     Thanks for your interest.                     PB

     Soeren,        Quite by coincidence we have also experienced some interference on 2.4. The plane is a ARTF high wing cabin job designed for glider towing. With flaps and tow release etc. A petrol engine, I’m not sure which one, but it is a specific model aeroplane lump. The radio is Futaba. My club mate, the owner, started it up to check everything out prior to a test flight. When the engine started everything went right off the clock, in every which way. The throttle was going up and down like a yo-yo too! So he thought we might be a good idea if we took a bit of a look at it. In fact, the effect was so pronounced that just flicking the prop caused the control surfaces to twitch in sympathy! Disconnecting the throttle servo lead from the rx so that we could control the throttle, it only needed to be on tick-over, we tried the easy things first.  We disconnected some controls in turn in case it was a rogue servo. No change. Moving the rx around as much possible, no change. I always keep an electrical first aid kit on board, soldering iron, wire, etc. so the next step was a bonding wire round all the metalwork and commoned at the battery negative at the rx. No change!!  Oh dear, beginning to run out of options. Looking for the batteries, both ignition and radio, it transpired they were tucked away in the fuz, with the two switches side by side under the side window. After a little tussle with the internal organs we managed to move the ignition batt a couple of inches. He’d made a good job of fixing them in, but, there was a definite little change in the air. Unscrewing the switch so that we could lift the battery clear of of the fuz, everything was as steady as a rock. Battery back in, mayhem!  Hallelujah! We’ve cracked it!!  We could actually watch the symptoms come and go as we shifted the battery around.      When I next caught up with him, the battery was installed under the cowl and the switch as close to the front as possible. And he was flying around, happy as a pig in clover. The engine, and radio, haven’t missed a beat since.     So what was going on here? I’m not at all sure but here’s a guess. I don’t know exactly how the capacitor in the CDI unit is charged up, a transformer, or some sort of oscillator diode pump perhaps, but I think it certainly would appear to make the ignition power supply a bit bumpy. This in turn induced some wobbles on the rx supply which it certainly did not appreciate. This was due to the close proximity of the batteries and (most likely) the wires running closely in parallel.     Certainly from this I think I would always ensure the complete integrity of both these batteries if I owned a similar set up. Good quality packs in apple pie order. The lower the internal impedance, the better. With possible hefty power surges like this, I also think I would be tempted to keep the ignition supply leads as short as possible, and if customising using heavier gauge wire. Definitely this one time we don’t want Mutual introduced to Inductance!     2.4 GHz radio certainly seems immune to r.f. interference but might it be slightly susceptible to the power borne variety? Under similar conditions to this, of course. I’ve never seen anywhere near this level of activity, other than when two tx’s on the same frequency are switched on together, on 35 MHz. This is largely supposition but there may well be a reasonable level of capacitance on the power input to a 35 rx, to soak up some of the ripples. But from what little I understand about it, 2.4 uses just the same two chipsets, and not much else.     It might well lend it’s self to a spot of tinkering about with, to see if this situation could be replicated.     Talking of rx batteries, I noticed the rx battery in this model, which is also the same manufacturer relating to another interesting development that I’ve recently done, concerning general levels of capacity. Or perhaps a lack thereof. But that’s another story….                We had a very interesting couple of hours sorting this out, made even better by the fact we’d found the problem. And hopefully, if anyone else’s elevator ever flaps up and down in sync with the spark plug, there might be a clue hidden in here somewhere.         PB     

    Thinking back to what I’d written in this thread, above, about the rx battery, I’m not sure that my explanation was completely clear with regard to the balancer unit. So with abject apologies for totally boring the electrical advisers I’ll try again.     If we take two cells, each with a capacity of 2,175 mAh, connect them neg to neg, and pos to pos, i.e. in parallel, then ostensibly we have a single cell, with a capacity of 4,350 mAh. Or a capacity of 16,095 mWh. If we then take another such pair, again call it a single cell and connect it in series with the first, then we double the voltage but the capacity in milliampere hours stays the same at 4,350. However, we have now also doubled the capacity in milliwatt hours to 32,190. Hence the reason for talking in watt-hours, sometimes it helps when comparing batteries of different voltages. Connect this to the charger and the balancer will just ‘see’ two single cells in series. This instantly explains why your balancer only shows two cells. If you charge two separate series packs in parallel to allow the balance unit to operate correctly the two balance leads would also have to be paralleled together. I would personally think that the more you can break a series installation down and charge the cells in parallel, the better.     It’s possible that I might have a modicum of confusion with balancer leads. I’m not greatly into lithium, and I don’t have any balancing units, but in my small collection of these batteries I have three 6000 mAh cells. These each consist of three 2000 mAh cells connected in parallel. Each unit has a balance lead but this seems to be a bit misleading. There are four wires, red, yellow, blue and black, terminating in a standard plug, implying that it is a standard balance lead, I suspect. But the red and yellow are common to the pos, whilst the blue and black are neg. It is physically impossible to ‘balance’ cells connected in parallel anyway. Or perhaps slightly more accurately, it’s impossible for cells in parallel to get out of balance in the first place. Therefore, if I charged this as a single cell I wouldn’t use the lead. If I connected two or more in series would I be fully aware of how to connect the balance lead?   I’ve only used these cells for experiments so far, but when these hopefully power a model, (in series), I shall make a three-branch charge lead and charge them in parallel. No balancer required!     Purely out of interest, I thought I’d kick your power plant figures around a bit. To swing that prop at any realistic speed, I think you’d need at least 2 - 3 kW, or around three really good hosses in fine fettle. Some of this is theoretical, and a bit of a stab in the dark, but the battery power capacity is 237.54 Wh, and if the flat out power consumption is 2.5 kW, then I would say the flying time is around 6 minutes. Probably up to 7- 8 with some low throttle use. How does this compare with what you actually get?     Pretty pokey stuff, not for the faint hearted, I guess.     Hope there is something of interest and I haven’t repeated too much that’s been stated before.                  PB    

Whilst reading this post it suddenly occurred to me that this battery is very similar to one that a helicopter flying friend was enthusing about some months ago. It was a high capacity lithium rx pack for helis. Amongst other things it had two pairs of output leads, in case one pair went faulty. I have a very slight problem with this logic, and I could only assume that each pair then had its own switch, followed by a voltage regulator and then on to the receiver. I wondered, too, if this was in some way to allay some fears about an old problem, particularly with receivers in helicopters. Some few years ago, when the digital servos first appeared, it seems that the extra load was causing the printed circuit board tracks under the servo connecting pins to burn up. The short term answer was to connect two switch harnesses to the battery and connect each one to either end of the servo plug slot in the receiver, to share the supply current. Perhaps another little example of just how far out of spec. aeromodellers can sometimes take their toys.  Id have thought, though, this problem would have been long sorted. This pack must consist of two cells in series, if you have a voltage reading of between 6 - 8 volts, with the other two cells also in series, connected in parallel with the first two.  Any other connection would serve little practical purpose, I would say. The two pairs of output leads are connected to the same point on the battery.  Each cell has a capacity of 2,175 mAh.     Total capacity, 32,000 mWh. Certainly a nice quantity in flying terms for a fixed wing rx pack, airborne all day and all night. And most of the next day as well, I shouldnt wonder. Could this be one explanation for this battery and thus a suitable sort of answer to this query?                           PB Edited By David Ashby - RCME moderator on 24/06/2009 08:25:27

    Hello Tony, thanks for your post. Not altogether sure about your charger intelligence statement, will it organise luncheon? Maybe it’s cooking your batteries to perfection, though? But, if it ever gets too upstroppilus you can always disconnect it!     Charging nickel batteries is the most difficult of the charging regimes to get right, with lead-acid being relatively more simple and lithium chemistry the easiest of all. My charger spends it’s life in the back of the car, connected to a 12v battery, charging or discharging someone’s packs. It has many variations of programs to choose from but when set to Auto you just tell it what type cell you are connecting and the charger then gets on with it. Up to 36 nickel cells, if you want. It also has a graphical output display, voltage against time, which is invaluable for fault finding. However, even this (super intelligent?,’cos it’s got a fair old microprocessor in it!), thing is sometimes thrown off course, particularly by nickel cells, see above, it thinks that it’s looking at one thing, when in fact it’s something completely different. The manufacturers are the first to admit this can happen, but as I’ve got well used to it over many years that does help to keep it on the straight and narrow. I’ve drawn a few conclusions about batteries, and many other modelling items, over time, and perhaps not all of them are by no means entirely satisfactory.     I’ve not had much luck on the Multiplex 2.4 front as yet. I’m still waiting for yet another bell which, like before, I’m beginning to conclude is not going to come. ’Twas ever thus. Still, I look on it as a challenge, perhaps MPX wish to know their customers will go through hell and high water to get their hands on the products. I shall not be disheartened or defeated! Although maybe a consultation with a trick-cyclist might be the cheaper and easier option!     Pleased to know you are in action ok, now we just need to order up a long, but not too hot, summer!                  PB    

    Just to try and spring in here and stretch another idea, surely the throttle control consists of a ratchet and pawl? The pawl part is a leaf spring, or flat spring, sometimes known as the indent spring, or perhaps just the indent. This flat spring has a little notch on it which engages with the groove on the ratchet.     To change modes you simply need to shift the flat spring over to the opposite stick and at the same time unclip the little cylindrical tension spring, this has a loop at either end, and attach it to the control from which you’ve taken the flat spring. As always, having the right tools does help, and a pair of fine long nosed pliers are invaluable. Needle-nosed are an even a better option!  I don’t think this is very difficult to do, but it can be a bit fiddly, and it’s easy to drop small bits into the innards of the tx.     There are slight variations on this, sometimes you can alter the tensions on how hard the spring bears on the ratchet, to suit individual preference, and sometimes the grooves on the ratchet are even removed, heli aces do this, I believe.         So it seems that everything has it’s own little spring, it’s just simply what you decide to call it.         I hope everything here has sprung into place, and this is in the right mode to be of some help.            PB          

     Tony -  Yes, there is a 2.4 coming, it’s called M - Link. Very tasty, amongst other things some of the receivers have Telemetry - Feedback with up to 16 sensors. Plus dual-receiver operation if required, I believe. Also, I understand, you can convert your tx, at the field, from 2.4 back to 35 in less than a minute. Or the other way, of course. I don’t know when it’s coming, but I suspect (hope!) any time shortly. In fact, I’ve been contemplating recently that I should be getting in touch with Germany to try and get up to date. It uses FHSS, Frequency Hopping Spread Spectrum technology, if that means anything. Also I’m guessing here too, but I reckon the binding process will be absolute bullet proof!     The cons. -  It will be expensive, of that I’m sure. However, once you’ve got your hands on it, it will instantly work, and still be working ok ten years later. If it’s anything like my previous kit, that is. And, as they say, life’s almost too short for carp fishing and dealing with Multiplex. You do have to be tenacious.     As an example of this, I’ve already tried to make some enquiries, locally, but I’ve not had any replies. But, if I do get a result in the near future, I’ll let you know.          PB  

  Hello Tony, -  Thanks for that. I only asked because I thought that if you were using a plug-in-the-wall-socket type you might run into some small difficulties perhaps. With the charger. But then again, maybe not.     I’m afraid I know nothing about the Hyperion, but I think I would be a bit suspicious about the battery voltage detect problem. Sounds as though that may need a light coat of looking at.     I’m not quite sure why MPX only recommend 150mA charge current through the plug.   I’ve owned a 4000 for years, I bought it in the Netherlands, before you could get one in GB, plus a Schulze 936g charger, at round about the same time. All a bit expensive, but I think worth it. I’ve also got some other useful kit, ex my working life, because I’ve been kicking batteries about and all sorts of other electrical bits and bobs for fellow modellers for as long as I can remember.     I charge my tx at a fixed 2A, because it has a 2A fuse in the charge circuit. It has a 3Ah, home made nickel hydride battery, about 9 years old. Still in perfect nick. The DIN plug configuration is exactly the same as the EVO, although the battery wiring could be marginally heavier on the 4000, but I don’t know. Maybe it’s just MPX being cautious. I think I would personally be tempted to bump up that 150mA rate, at least a little tiny bit. Or even a tiny little bit more than a little tiny bit!       Another point of interest perhaps, I’ve checked out tx and rx packs on a safety basis for many years, using my own fairly tight spec. Very recently I had a date with a JR tx. I’ve hammered it before, but it’s always passed. This time it failed to reach the standard, and it’s also got the first signs of a little dollop of the black wire blues. It’s the original Yuasa nicad pack, and it’s now 33 years old. The owner has said that, up until now, the whole caboodle has never given him a moments concern. They just don’t make ‘em like they use to!     Please let us know how you get on.  Good Luck.   PB     PS. A very quick look at MPX site says EVO can be fast charged.  That’s with a new 2100 mAh batt. And that must be via the DIN, surely?  

    Tony -  A pleasure!   These connectors can be confusing, there may well be up to 15 configurations of DIN. Plus all the countless other types, and their many variations.     Just out of interest, and if it’s not an impertinent question, can I enquire please, what you are using as a charger to charge the battery?     PB

     Tony,    Hopefully here are the MPX battery charger connections. Looking at the DIN socket on the back of the transmitter, with the polarising indent at the bottom, then you should see a 7 pin circular array. Starting at the bottom left, number 1, and going clockwise, then number 2 is the battery positive and number 6 is the battery negative. A standard 3 pin DIN plug, Maplins,HH 25C, 19 pence, is what you need for connection. If you are not completely confident here then looking into the 3 pin plug from the front, and again with the polarising peg at the bottom, connect your positive charger wire to the RIGHT HAND pin. The top centre pin is not connected.          All Multiplex radios have this standard arrangement.     I hope this is what you were looking for.       PB                

            Andy,    Thanks for the reply.     So then, for the next person that wishes to shine a little light into his electrical darkness, I’d have to say that I think there would be very little difference in installing either system. In fact, the lever operated roller version may be the better option regarding the micro switches, they are used in many varied applications, and with helpful functions like ATV on the tx controls you’d get lit up in no time at all! Vibration is never going to be a problem, with either set up, if it were, the tail-plane has just been shaken off anyway!          Just to continue Phil’s theme awhile,or should that be Polyamplified, maybe even Polytwyceamplified, the op-amp was originally designed for the early computer industry, I believe, but it’s now become one of those universal gizmos that everyone finds a use for. In my case, I was using it as a comparator, comparing two voltages. It’s rather good at this, it will change state, i.e. switch on and off, or more strictly, go high or low, with a change in voltage level, or differential, of just a few thousandths of a volt. Or even just a few millionths. You can find it at the heart of your actual voltage regulator, the somewhat oddly named BEC, so beloved by all the aficionados of electric flight. I had in mind a switch for on board glow, you can build in some hysteresis, which is the lag between you doing something and something actually happening. In my case, that can be a long time. It was intended that it would turn on the glow at low throttle, but not switch it off until the throttle was more than half open, or so. I never did get around to it, though, and now, of course, you can buy commercial units that do that, and more.     I think that op-amps, like many other modern electronic components, are generally very precise, have a working life almost to infinity, and as is oft quoted, as cheap as chips. They also seem to be almost unbreakable, within their operating parameters, and indeed, sometimes even substantially outside those limits.     Good Luck with your endeavours.                    PB.       

       Gentlemen - I’ve just picked up on this thread and I wondered if I could make a couple of observations, hopefully without butting in.           Leaving aside the pros and cons of a direct connection of any miscellaneous devices to the receiver battery, and I wouldn’t compromise the radio system by doing that, but that’s purely my own personal choice, why not simply switch the 12v supply to the two items. Could you not do this using a complete, normal servo and a micro switch? Then it simply becomes a mechanical job. Maplins do a few such items, the GW69A at 99p looks good. Will switch 2A, plenty of scope. Don’t know the weight, but it’s surely only a few grams. Mount the switch so that the arm operates the lever at full travel. You might need to be reasonably accurate here, making sure the servo is not stalled etc. The switches require very little effort to operate anyway, and with a bit of ingenuity you could build in a small degree of adjustment. Or you could mount it remotely, operated by a push rod perhaps. Indeed, if you don’t ever want to turn the siren and the landing light on together, you could have the other switch at the other end of the arm travel, operated by a tx rotary switch, or a 3 position lever switch, if you have one on the box.     An alternative, slightly up-market answer might be to substitute reed switches. And they are really light! They are just small sealed glass tubes, with contacts inside, operated by bringing a small magnet near them. Again the engineering might have to be fairly precise, but because there would be no load on the servo you would have a degree of tolerance. For instance, you could make a longer servo arm, or a tailor made shape, glue the two little magnets on the ends and you’re  in business! Maplins, CL38R, £1.29, switching 1A might be a fair bet. Or the N31AN, switching 2A, at £2.29, perhaps. Magnets from Maplins, £1.49, too.     Now you’ve got 12v to the landing light, you’ve got a bit to play with. And you don’t have to consider the rx pack. I’ve have thought, for a landing light, you’d need a nice, bright, white light. I think I would be looking around for the brightest I could find.     Incidentally, it is possible to make a small and very light electronic switch, using an op-amp. This is probably the most elegant solution, but you do need to be very familiar with a soldering iron. And a multimeter. I saw a design years ago, so I made one. As it so happens, all the component values I used were completely wrong, ‘cos they were all I had on the bench at the time. But, stap me, it worked! I was so surprised I nearly bought my own beer! By using a good quality output FET it could be used to switch quite a few tens of amps.     Hope this is a positive?? suggestion.    PB.   

    Olly,         Thanks for confirmation             I do feel that if I owned the type of transmitter that requires modification, I would think very carefully about doing it.     I’m slightly nervous that I might find myself, although perhaps most unlikely, in a situation where I might have to very robustly justify my actions.     And even that might not prevail!           Could be tricky!                             PB.

    I think that I would tend to assume that, although the battery is a user replaceable item, unless you replaced with the manufactures approved item, you might still render the CE Certification null and void. If the manufacture has not approved the battery replacement type i.e. lithium polymer, how would it have obtained certification in the first place? Surely it has to have the battery installed to be approved?         I asked a Legal Beagle for his opinion on all of this, a long time back, and, as always in the ways of lawyers he was suitably vague. However, he was fairly candid about the fact that any doubts or misunderstandings would undisputedly be settled in any Court case. And he was also totally convinced that, in the event of there being a very substantial claim, the insurance company would look at it very carefully indeed. They would spot a loophole from the other side of the galaxy! And, indeed, they are certainly not renowned for being benevolent.     Would it be an idea perhaps, to show a modicum of prudence if you have carried out these mods, and contact the BMFA, and the insurance company, informed them of what you have done and get their express approval, in writing?     Or perhaps a trifle less expensive, to ask these parties if they will approve of your changing the specifications, before you actually do it.     I’m told that even something as trivial as changing the wheels and tyres, or less, on your car, can, in extremis, cancel your car insurance, if you don’t tell them you’ve done it.     I think the BMFA is carefully trying to say that tinkering with your transmitter is Not a Good Idea.        Could be the makings of a Decent Debate here, I reckon.   PB.

     Myron,         I’m still not convinced that you can judge the capacity of a battery by what you put into it. I prefer to check what you can get out of it. If you charge a flat battery at the 10h rate, or 1/10C, for 16 hours and then discharge at 1/10C this will give you an indication of the true capacity. But there are caveats. I suspect that it is very difficult for most modellers to charge just any battery pack at exactly 1/10C, for instance a 2600mAh pack requires a constant 260 milliamps. Will your normal field charger be able to do this? I’ve not had a lot of experience with basic chargers, but from what little I have they do seem to be fairly limited. The same may apply to the discharge, so straight away we have to start making allowances for the compromise.     With regard to to the wall charger, as I said before, it’s always wise to check the output, fairly accurately if possible. The first problem, if you plug into the tx, is that you are charging via a diode, and which ever way you look at this, it is always going to lower the battery voltage by around 0.6 volt. As you say, you can do the maths, my version to charge your 1000mAh batt would be 1000 + 60% ÷ 70 = 22.8 hours. But is your charger delivering a constant 70mA? I think I would be surprised if it was. We have the afore mentioned diode working away, and you also seem to have a watt meter in circuit. Doesn’t this give you the charging rate? If the rate is closer to 40mA, say, then that would make your 500mAh in 24 hours a trifle more realistic. Again, as I said before, I’ve not been able to play with these modellers’ watt meters. I did look at the spec. of the ‘Watts Up’ meter and that gave the shunt resistance of 0.001 Ohm, which is nice and low, but what is it’s total resistance when in circuit?     Looking at the nicads, I wouldn’t think there are too many problems there. To quote an actual example, I had some 16 cell, 1.7Ah nicad packs in a Simprop Diamond. My charger, which is one of the clever types, checks out the pack it’s charging as it goes along and then adjusts it’s charge rate accordingly. When the pack was hot, after flying, it would charge at it’s max, 10 amps, which is around the 10 minute, or 6C rate. The discharge, which was usually in 4 - 10 second bursts at a time, was a total of around about 3/4 minute per flight, in total. This could vary quite a lot, though.  This might equate to a discharge rate of up to perhaps 70 - 90C. The cells seemed to generally cope quite well with this, although over time I did burn out two individual cells. I repaired one of them, and then used it as a glow driver for a short while, just to prove the point. As it so happens, this is just one of a few reasons why I’m definitely not a UBEC man, but that’s another story...       Hope this is of some use.                      Pete.