LiPo RX Regulator causing Interference

[Myron Beaumont]

PS  to Mr Ashby

PLEASE provide me with a wooden spoon "smiley"

[Peter Hawtin]

Timbo - forum moderator wrote (see)

Peter Hawtin wrote (see)

Of course not doesnt everyone charge their LiPo's in their Airframe? 

Mine are charged on the dinning table in the lounge where I can see and keep an eye on the charging rate.   I also estimate how long I feel they will take to charge and use a small kitchen timer to remind me to check they are done.

 I also use a temp monitor on the charger to kill the charge if it goes over a pre-set limit.

 Wife hates all the mess, but at least I know if there is a problem. 

 Peter

You estimate how long they will take to charge - Why? Any proper dedicated Lipo charger will use the correct constant current / constant voltage method to correctly charge and determine the terminal voltage and stop the charging process. If the packs are accessible to be able to insert the temp probe, then why not just remove them any way and charge outside the model - this is the safest method, as it also allows you to see if any cell is starting to puff.

Timbo, i think you missed my point, I never charge LiPos in my model, hence the reason I can charge them on the dinning table.

 If you think that a charger can never go wrong you are very mistaken. In just 3 years of flying on LiPo powered models I have had a charger go crazy.

 I have just invested in a Groupner Ultra Duo Plus 50, and even with a charger of this quality I keep a very close eye on the packs being charged.  I also never discharge a pack more than 75% of its capacity, as this keeps the Pack in good condition longer, and as some of my flight packs are close to £300 each, I want them to last!

 I have today designed my own LiPo voltage matcher(so easy should of done it before), and the prototype ran 6 servos, three of which were loaded with 0.5kg on long servo arms, that roughly equated to around 5kg at 1cm.  Using a 2100 LiPo 2S pack, it happily drove all six servos for well over two hours, with the final LiPo voltage reading 7.2v. That equates to a 1ah average servo drain, over the two hours.

My largest model uses 7 servos, 6 of which are 8 - 17kg digital, units. So I dont think I will have a problem when using two parallel 2100 2S packs.

 The unit did get warm, and under high load with the servos close to stall, some of the components were just over 55deg C, but when I have both battery packs working the load will halve, cutting down the heat. That said 55deg C is nothing to worry about.

Peter

[nasa_steve]

"but the 30 ft range check was fine "

  that is certainly not a range check a range check should be 30yards minimum and even that is pushing it a little. that should also be an ariel down check as well ,30feet you may as well not bother  at all and you have unfortunately proved it was not enough......lesson learned i hope and glad noone was hurt.

nasa

[Peter Hawtin]

The model had had a 50mtr range check the day before. I had done a capacity check over night on the old RX pack and it only had 60% capacity.

 I switched out the 5cel RX pack and used an 800Ma 2S pack through the regulator.  I only did the 30ft check with the aerial removed as a way of ensuring all was well and movments were OK.

I really did not think and for that matter neither does the majority of experienced modelers tI have discussed this with think that an RX battery pack through a product designed for the purpose would have such catastophic failiure.

 This was not just a few glitches, it was stop to stop movement on every channel.

 Peter

[Tim Mackey]

When asked by Tom whether you were joking about charging your packs in the model you replied

"Of course not doesnt everyone charge their LiPo's in their Airframe?"

I think my conclusion that you charge within the model was to be expected. 

[Peter Hawtin]

I did put a big smily face after it  

Sorry my friend, my humer can be a bit dry sometimes

Peter

[Tim Mackey]

No - actually you put a " surprised " smily after it - this has a different conotation altogether.

Perhaps the proper one to have used would have been this

Perhaps even better would to actually state clearly that you were joking, especially as this is a rather serious matter, and we are all striving to help newbies with the already confusing and mystifying subject of leccy flght.

PS if you hover over the forum smilys they state the meaning.

[Peter Hawtin]

No they dont..at least not when using Firefox!!!

And yes we did ramble off the subject a bit.

 OK suitably chastised 

 Peter

[Nik Harrison]

Just for the hell of it I tried the "hover" bit.  It works!!!

I'm also using Firefox. [This one is called "smile"]

[Peter Hawtin]

Strange...Well I cany blame Mr gates as I am using Linux.

 Mine gives ma a message about Java Script Void

Peter

[Tim Mackey]

I also use Firefox and it works fine here too. Anyway, no need to drag it out any further, you are forgiven

We are after all, the friendly forum. Back on topic.

[Andy Gates]

I tried a couple of stand alone BECs a few years back, and they all caused exactly what you saw on your model - stop to stop glitching on all surfaces. Lucky for me I picked this up during first stage reception testing at home going through 2 walls.

I have binned them and stick with the weight penalty of the Rx pack. Rather a machine that takes a few extra feet to take off than one I can't control.

Sorry about your model but that is what happens when we take short cuts of get flustered at the flight line. I managed to fly a plane with an aileron servo cover and mount fastened with only 2 screws half way in, the plane survived - lesson learned!

[Bev Lawton]

You need to enable Java Script implicitly within the Firefox Browser to enable Java Script thingies" to work.

This explains all : http://support.mozilla.com/en-US/kb/Options+window

but basically you click the TOOLS tab in the Top bar - select OPTIONS in the drop down and then select

the CONTENT Tab. You will find the JavaScript and Java boxes in there. 

I use Firefox but just for the hell of it I tried the AOL Browser and that doesn't show the meaning of the smilies when hovered over - thats not really a suprise as AOL is not Java enabled unless, again, you implicitly enable Java Script.

 Bev

[Peter Hawtin]

I have binned them and stick with the weight penalty of the Rx pack. Rather a machine that takes a few extra feet to take off than one I can't control.

I have to ask why you binned them and did not return them.  I am amazed how many of my club members say the same about flying products they have purchased.

 It used to be ARTF manufacturers that ripped us off, now it the accessories, we need to complain and complain loud when products dont work.

I have found a voltage matcher that does not use switching, and cost far less that others.

Peter

[Andy Gates]

Reason they did not go back to the supplier was one of them would have to go back to the USA and the cost of the unit was less than the postage. The other was a bargin bin item, so again I could not really justify taking it back & complaining.

Shortly after I got the USA one, I found a few write ups which said much the same about the product as I had found. The product was removed from the website shortly after.

As far as the ARTF thing is concerned, I have never had an ARTF machine. Sure I have flown a few planes that were owned by others, and they flew well almost without exception. They don't take abuse (especially heavy landings) very well, and I have seen a good few undercarriages wiped off by poor landings, but is this really the fault of the planes?

Excluding these items, almost everything has worked as advertised until I abused them. My fault then

[Tim Mackey]

>>I have today designed my own LiPo voltage matcher(so easy should of done it before), and the prototype ran 6 servos<<

Peter, when you say you have designed your own "voltage matcher" what exactly are you meaning here - and if it is so good, why not share it with us?? 

[Peter Hawtin]

The circuit is one used in cars to match 12 volt power to 6 volt electronics, as there is no switching involved, there is little noise at any frequency. 

I am doing some testing on it, so far its happy on 6 servos, three of which loaded were to 600g on a 35mm arm (about 2 kg at 1 CM).  This test was run with the servos all continusly cycled for two hours.  I then stalled three servo with a big load and apart from the servos getting hot, the matcher worked fine. All told the simulation was an attempt to match the sort of loads a freestyle model goes through in a flight.

 It was an interesting test as the 2100 2S LiPo only used 1400ma during the whole test. I have repeated the test with 1kg on the same arms, for 30 mins and apart from the matcher getting a bit warm, all was fine.

 I need to do some over load tests to see what happens if some how all servos get stalled.

 Peter

[Tim Mackey]

But what exactly is this device - surely it is just a regulator, and probably just a linear one at that ?

[Peter Hawtin]

It does not regulate, just reduces the voltage.

 Simple, reliable, and can not effect the radio signal.

 Peter

[Tim Mackey]

Then as I say.... if its so good why are the trade not selling it too us ?

If its not a simple linear regulator, then it must be some kind of resistor based voltage divider....also known as a potential divider as in the picture.

These are extremely inefficient and waste a LOT of energy as heat.

You say you have designed this device....please tell us more !

[Brian Parker]

Or perhaps a high dissipation zener diode.

[Tim Mackey]

Yes, but still a pretty inefficient way of "regulating voltage" and also current limiting I would expect.

[Brian Parker]

Agreed!

[Bert]

I made a linear jobbie with 2 LM2940CT regs in parallel to run off 2S Lipo.

The LM2940CT is a low-dropout (0.5 at 1A) reg.

2 in parallel gives 2A - seems to work for me

Bert

[Tim Mackey]

Well yes it would, but we are straying off the question addressed to Peter here, just exactly what is his own design "voltage matcher"