Telemetry - do you use it? What do you think of it?

[Richard Wood]

Does not surprise me. The current 'advanced' Telemetry kit is far too expensive.

Some examples on measuring current consumption:

Hitec - To measure current consumption on the, you need all this: Hitec Telemetry Blue C50 Combo - almost £50, not cheap enough to put on every model. Not only that, you have to fit all those extra wires and sensors over everything.

 

Multiplex - You can buy a inline current sensor that plugs directly into the receiver - Multiplex 35A Current Sensor - a reasonable £30.

 

Spektrum - No current sensors yet available. Mostly Vario sensors.

 

Futaba - From what I've seen, it ;ooks like you will need Futaba's expensive ESC initially. Neat solution to have the current read directly out of the ESC - however I can't imagine it'll be cheap.

 

Jeti - Additional current sensor like Multiplex Jeti Duplex 2.4EX MUI 75 Sensor - 75A sensor for a very reasonable £28. However Jeti have no transmitters yet and requires an existing module based transmitter. Also you have to have a screen tagged on the top of the transmitter, like Futaba's FASSTest system will be.

 

Graupner - I can't see any current sensors. Appear to be mostly Vario sensors.

 

So really there isn't that much out there. What there is, it is quite expensive. Note that none of these solutions are cheaper than buying a Watt-Meter. A Watt-Meter is actually more expensive to produce part wise than any of these additional sensors!

 

Yes it is quite expensive but does that explain why Germany has taken to Telemetry

& the UK & US haven't (yet)?

Is this stuff cheaper in Germany or are they just prepared to spend more on

their hobby than the British & Americans?

 

At least Rx pack voltage is integrated & flight pack voltage only requires

two wires - these alone could be quite an attraction for many.

 

Let's hope the prices of the more advanced stuff comes down as it gets

more established .

 

 

 

 

[Steve Hargreaves - Moderator]

I wonder if its because the Germans have a more "engineering" based population & they are more interested in what's going on in their models......

 

I work for a German company & speculation & opinion is just not something they do....it must be backed up with hard data & facts.....there is no phrase in German for "ball park figures".... Any such request I make of my German colleagues is met with blank stares of incomprehension......"Ve must make a test before we can say......." is the standard response.....

[Andy Palmer]

I bought a Multiplex Cockpit when I switched to 2.4 last gear partly because of the top mounted screen and the telemetry capabilities. So far I haven't bought any additional sensors so I just have the rx battery voltage and link strength that are standard. The link strength always seems to be on 100% so I rarely even look at it now.

 

When I first installed the new gear in a plane I had been flying for years it took me a while to figure out while the tx kept bleeping at me. Then I realised it was the rx battery voltage alarm going off each time I did a manoeuvre that put a bit of a strain on the servos! I had regularly checked the rx battery with a loaded meter and it seemed fine. But having telemetry that showed me how much the voltage was dropping at certain times in the air convinced me to replace the pack immediately.

 

One of our club members had a model crash recently and discovered that his rx battery had died. Like me he had checked the pack regularly but not realised there was a problem.

 

So for me I am very happy to have telemetry and when funds permit I will buy some more sensors. I fly electric so a current sensor that tells me how much is left in my power pack and alarms at my chosen remaining capacity will be great and more accurate than using the throttle linked timer I use at present.

[David Ashby - Moderator]

Posted by Steve Hargreaves on 10/02/2012 11:54:32:

I wonder if its because the Germans have a more "engineering" based population & they are more interested in what's going on in their models......

 

I work for a German company & speculation & opinion is just not something they do....it must be backed up with hard data & facts.....there is no phrase in German for "ball park figures".... Any such request I make of my German colleagues is met with blank stares of incomprehension......"Ve must make a test before we can say......." is the standard response.....

 

 

Yes, should have said but the distributor seemed to agree with you Steve, the Germans like their data and seem prepared to buy the widgets to provide said data.

 

 

 

[XMB]

Graupner do have a module that measures the battery current and voltage along with connectors for optional fuel level, temperature and RPM sensors for about £40. (Model no. 33610.)

This module is compatible with their new HoTT systems (MX-12, MX-16, MX-20). Interestingly these transmitters have some of the best telemetry support I can see including all radio signal data and even the individual cell voltages of Li-po packs when used with the above mentioned senso module. All this data is stored on the SD memory card so it can be reviewed after the flight either on the TX screen or via the PC software. Of course alarms can be set for almost any event and the transmitters have a speech audio output to relay the data and alarms (to a earpiece). Seems very comprehensive and quite a good price as the 8 channel MX-16 costs about £300 with TX and RX and includes the SD card and PC USB data cable.

It is odd no one ever seems to mention this radio! But maybe, as others have said, telemetry is not of interest to those in the UK and USA?

[ntsmith]

Here's a story: (and a thought!)

The other day I crashed by beloved 48" Vanquish. After the crash the flight log (on the transmitter showed a lowest receiver voltage of 3.9v. I imagine it went lower than this and caused a "brown out". I had flown it a lot but that day was about the fourth or fifth flight with the added telemetry module and I take it that it may have been that which was the straw that broke the camels back. It was on that last flight that I was practising some flick rolls which take quite a bit of extra power from the servos so I am not sure if it was the telemetry module addition or if it was the added load. I little of each I suspect.
I later found that there is an alarm on the DX8 which would have defaulted to 4.5v - had it been activated, so the fact is that used properly (not like I did) it can save a model. The fact that this one didn't get saved was because the system was new and I was unaware of its capability.
I had recently changed my transmitter from a DX11 back to a DX8 which I loved and decided to return to but as I said, wasn't fuly conversant with its capability but it has made me a firm believer in telemetry systems; its yet another fail safe that if used properly can save your aircraft.
I put it down to experience and I hope I and others can learn from my mistake.

[Frank Skilbeck]

Interesting point, I found the same when setting up a model on the bench with a well used Rx pack, the telemetry alarm kept going off and I only realised this was when I was moving all the servos together.

I did some in flight tests and found that with the motor off I can get 0.7A pulled from the flight battery when using all the controls (on an Easy Star ). I don't think the telemetry itself adds any appreciable load. The telemetry though has made me much more comfortable with the BEC function on ESCs, the voltage is completely unchanged asthe load changes (within the design of the BEC), much more stable than a regular flight pack.

[Keith Emerson]

If you go back to my posting re my Habu 32DF crash (somewhere on page 5 of this thread) You'll see that I had the same experience (and even used the same words i.e straw & camel's back !)

I'm not sure that telemetry would update often enough to see the momentary voltage drop which I suspect is all that is required to reset the Spektrum rx. Even on the bench you'd probably need a storage scope to see the momentary voltage dips as loads are applied. As stated (in my opinion) its much safer to fly with a separate rx battery or BEC and set it to the highest voltage the rx is specified for.

[XMB]

If you are monitoring the motor battery voltage and not the reveiver voltage, which will be always showing the BEC voltage, then you will get a indication of a problem long before the reviver voltage drops below the minimum value. Of course you have to ensure the alarm is set at the correct level for the type of battery in use otherwise the monitoring is useless!

[ntsmith]

As I stated it was the Receiver voltage and had I paid attention to it my crash would not have happend. Regarding update speed it still would have shown the very low voltage that was being seen at the receiver as it was an average voltage that it had fallen to and I agree always use a seperate BEC particuarly with more than four servos.

[Andy Palmer]

I have no idea of the update speed on my Multiplex system but as I said in my earlier post (10/02/12) I am happy that the telemetry showed up a failing rx pack. Bench testing it showed the alarm bleeped the second I stirred the sticks, yet a battery checker showed the pack as ok to use. Since buying a new larger rx pack the alarm has never bleeped again

I am also flying an EDF that uses BEC and the voltage always shows as being fine and the alarm has never gone off, even when I have run the pack right out. I use A123 cells so if I (inadvertantly) fly until the pack voltage suddenly drops too low to power the plane the cells are not damaged.

I haven't bought the Flight Recorder yet so I can't analyse the voltage after flying but am very happy with the extra safety the built in rx voltage alarm gives me.

[Keith Emerson]

From what I can gether from other experiences posted on various web sites the Spektrum receivers are particularly susceptible to "brown outs". In my case it was a full receiver reset ending up with my elevators (although connected on a "Y" lead) operating in different directions.

[Andy Palmer]

Ouch!

[ntsmith]

Dont want to get into a rant about spektrum receivers. They are great but what else would you expect at 3.7v. I dont think theres much that will work out there, When the voltage is gone its gone - on any radio !

[Andy Palmer]

I agree Nigel,there are lots of other forums where you can read about Spektrum rx problems

[XMB]

We are going a bit off topic but maybe we should all be adding a capacitor to the receiver supply to try and iron out any dips?

I see the Graupner range of HoTT receivers (GR-16 etc.) quote a supply range of 3.6V to 8.4V and remain functional until 2.5V! They also say they have a fast re-binding time but give no figures. Maybe it is time all radio manufacturers provided re-boot and re-bind times in the event of a power brown out?

[ntsmith]

Spectrum state themselves that the capacitor is specifically meant for ground vehicles and is NOT to be fitted to aircraft. Cant see their reasoning myself but I never fit one but aim to keep the voltage to a level that is high enough not to warrant problems. IE use a 6v system where possible and if a 4.8v system then a max a four standard servos and check the voltage by applying some force to two or three of the surfaces at once to simulate a high load and check what it drops down to.
Spektrum now have a very fast rebind time but this is all off topic. The topic is Telemetry and in short I would only under exceptional circumstances not use it.

[Andy Palmer]

Posted by ntsmith on 20/03/2012 07:31:46:

in short I would only under exceptional circumstances not use it.

I agree. For about £15 more than a standard rx I can buy a telemetry rx that gives me battery voltage and link strength for whatever model I use it in. Over the life of a receiver that could be a lot of models and if it saved just one that would be money well spent. Plus I have the option to purchase extra sensors for whatever info I require. A current sensor acts like a fuel gauge on electric models and gives a readout of what is left in the flight pack and gives an audible alarm at whatever level is chosen.

[Martin Oldershaw]

I recently had to upgrade my radio for more channels as I got more & more in to the large scale glider scene. I have been a JR/Spektrum user for several years but am not over impressed with the Spektrum prices and features on their latest developments. I did extensive research and settled on the Graupner MX-20, mainly because of it's features and telemetry data and very reasonable price when compared to the competition. As this thread is about telemetry let me say what I like about it.

The first main thing is I don't like the idea of live telemetry data is if you have to read it, even with a glider at 5m wingspan I do not want to take my eyes of it at 400 plus meters in height so spoken data to me is a must and the Graupner Hott system offers just that. I use a GPS/vario sensor that plugs in to the reciver and with headphones plugged in the transmitter I get 5 tones up & down of vario and at a flick of a switch a list of spoken data. You can program in how much data you want but main ones are altitude, speed, batt voltage real time and lowest reached (tran & reciver), signal quality, gps heading, receiver temp and so on. I love this data whilst flying, some of it is obviously a real help in making the most of thermals.

I know we don't all fly gliders but there are a number of other modules available to suit data required in other types of flight. All the data is stored on a SD card and is really quit fun viewing it later on your PC, including a Google satelite image map showing a trace of your flight.

Having now used telemetry I would not want to buy a set again without it but let's face it, we can still very much enjoy our hobby without it.

[Martin Oldershaw]

I recently had to upgrade my radio for more channels as I got more & more in to the large scale glider scene. I have been a JR/Spektrum user for several years but am not over impressed with the Spektrum prices and features on their latest developments. I did extensive research and settled on the Graupner MX-20, mainly because of it's features and telemetry data and very reasonable price when compared to the competition. As this thread is about telemetry let me say what I like about it.

The first main thing is I don't like the idea of live telemetry data is if you have to read it, even with a glider at 5m wingspan I do not want to take my eyes of it at 400 plus meters in height so spoken data to me is a must and the Graupner Hott system offers just that. I use a GPS/vario sensor that plugs in to the reciver and with headphones plugged in the transmitter I get 5 tones up & down of vario and at a flick of a switch a list of spoken data. You can program in how much data you want but main ones are altitude, speed, batt voltage real time and lowest reached (tran & reciver), signal quality, gps heading, receiver temp and so on. I love this data whilst flying, some of it is obviously a real help in making the most of thermals.

I know we don't all fly gliders but there are a number of other modules available to suit data required in other types of flight. All the data is stored on a SD card and is really quit fun viewing it later on your PC, including a Google satelite image map showing a trace of your flight.

Having now used telemetry I would not want to buy a set again without it but let's face it, we can still very much enjoy our hobby without it.

[Martin Harris - Moderator]

While flying my faithful Chipmunk today (first model I built when I returned to the hobby 10 years ago) I became aware of a beeping sound. Decided I'd better land and investigate without further delay...

This model has a first generation Jeti receiver which only displays a single pre-selected parameter on the Jetibox (but beeps warnings for others not displayed) and I only knew that the model was receiving a decent signal...landed and checked through the parameters and found the receiver voltage was 3.6V (dropping to 3.4V when all the sticks were waggled - the voltage held so it looks likely that a cell in the NiCd pack has failed).

This is why I like using:

(a) Telemetry

(b) Receivers that are designed to work down to 3.2V (certainly proved to work glitch free to 3.4V)

(c) NiCds which typically fail short circuit

While I accept that I should always check the pack voltage before flying, this failure occurred during flight and probably (without telemetry) if it had survived the day unnoticed, I'd have spotted the low voltage on charge if I'd recharged with an intelligent charger as usual but if not, the best case scenario would be a wasted trip for it on the next session.

Edited By Martin Harris on 28/09/2012 01:27:13

[Kev Greenwood]

I bought into it thinking it would warn me when the main flight pack is down. I think (and i maybe wrong here) that it only monitors the volts, not amps, i was using it on my extra 330 with a 6s, max volts 25 min 22.5 which i set manually (default is 19v) after 50% of the battery has gone, if i use full throttle, the alarm sounds low volts. Ive been told its because its measuring volts on load !!!! i must admit i dont understand electrical systems at all, i just fly......so i use the timer. 11mins and after checking the batter on my tester, i end up landing with 20% of battery left which equates to 22.2volts, this is why i set it to 22.5 so it would give me 60 seconds to setup for a landing. But like i said, using the throttle aggresavly, it activates the alarm because its pulling the volts down below 22.5v.

. I was trying to set the telemetry so that it would warn me at this level, but it dont work like that......well i dont think so anyway. I reckon if i ran the battery to the default volts (19) im sure my ESC would shut down before that........forcing me to land without any motor power. I still think the DX8 is an awesome set.....very accurate, i fly every plane i have on full rates....

If someone can explain or give me some type of setup so the telemetry does what i want it to do, would be appreciated.

Kev

[David Ashby - Moderator]

Martin - a very good example of the benefits for sure.

[Frank Skilbeck]

Posted by Kev Greenwood on 03/11/2012 06:48:56:

I bought into it thinking it would warn me when the main flight pack is down. I think (and i maybe wrong here) that it only monitors the volts, not amps, i was using it on my extra 330 with a 6s, max volts 25 min 22.5 which i set manually (default is 19v) after 50% of the battery has gone, if i use full throttle, the alarm sounds low volts. Ive been told its because its measuring volts on load !!!! i must admit i dont understand electrical systems at all, i just fly......so i use the timer. 11mins and after checking the batter on my tester, i end up landing with 20% of battery left which equates to 22.2volts, this is why i set it to 22.5 so it would give me 60 seconds to setup for a landing. But like i said, using the throttle aggresavly, it activates the alarm because its pulling the volts down below 22.5v.

. I was trying to set the telemetry so that it would warn me at this level, but it dont work like that......well i dont think so anyway. I reckon if i ran the battery to the default volts (19) im sure my ESC would shut down before that........forcing me to land without any motor power. I still think the DX8 is an awesome set.....very accurate, i fly every plane i have on full rates....

If someone can explain or give me some type of setup so the telemetry does what i want it to do, would be appreciated.

Kev

Kev

Yes using voltage om a flight pack to determine the mah left is not fool proof because of the effect below, as the battery runs down not only does it's off load voltage decline but also the voltage underload, most ESC tend to cut the power when the voltage per cell drops below 3v (2.85v) in my case, so they cut when you try and put a load on the battery, so having the alarm set at 22.5v is too high and between19 and 20v is probably a better value as this will still give you time to land.

I must admit I use my telemetry set up to record the mah used and have a countdown so it alarms when I get to x mah left (I have to input the battery capacity first) and I use this now instead of a countdown timer

[Bob Cotsford]

Posted by David Ashby - RCME on 03/11/2012 07:18:30:

Martin - a very good example of the benefits for sure.

I'll second that as I lost my Katana in exactly those circumstances - the battery monitor was in the green before take-off, but the pack voltage dropped off a cliff in mid roll and the model continued rolling on to the scene of the crash. That was with a pre-telemetry FrSky receiver that would work down to 3v, so I suspect the servos ran out of power first. Nowadays I use receiver voltage monitoring as minimum on IC models of any size.