Possible actuator problem

Waggly tails
Tobe
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Joined: 16 Feb 2018, 06:19
Location: Varberg or Stockholm, Sweden

Re: Possible actuator problem

Post by Tobe »

Glitches, if they appear to what I have found, are when I supply power via a voltage regulator/power supply and not via a battery pack of at least 4s NiMh / 500mA. Power to the receiver/ ATtiny85 is not critical but supply to the actuator is, see earlier post from Phil.
viewtopic.php?f=25&t=599
The main issue is to find a solution for what is out there and those having glitches w/o the necessity to run from batteries instead from a ESC
Cheers,

Tobe
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Mike_K
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Joined: 16 Feb 2018, 06:35
Location: Hertfordshire

Re: Possible actuator problem

Post by Mike_K »

Hi Tobe

The Tobe Rand is currently in a glider (Veron Impala), so all my tests have been with a Panasonic Eneloop 2000mAh 4 cell AA battery pack (bought new in Sept 19), not an ESC. But I've been getting the occasional glitch with that setup, albeit with an Arduino Pro Mini, not the original (I blew that up putting far too high a voltage on it if you remember) and probably too stiff linkages.

But with the modified Arduino program, it does work flawlessly with a single battery and the stiff linkages, I probably posted a misleading picture and didn't make myself clear.
Tobe Rand driver modification
Tobe Rand driver modification
The main thing is to copy the method that Martin is using with his driver i.e. separate the motor on/off from the motor direction and to stop driving the motor for the last 10% (and letting it keep moving under its own inertia) before changing its direction. And as I've said, it has other benefits as well, such as returning to near centre when there is no Rx signal (a type of failsafe), less power consumption etc etc.

I've been in my workshop for much of the day and have had it running continuously without hearing any glitches. I've then connected the enable and phase back together, reverted to the old program and within five minutes there's the odd glitch again. I'll change back to the enable and phase pins separated and try powering it with an ESC to ensure it works OK with that.

There is no additional hardware needed (besides the additional wire from the ATtiny85 to the DRV8838), so it's a very straightforward software modification.

Once I've tidied the program and I've tested it on an ATtiny85 I'll post the modifications.

Cheers

Mike
Tobe
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Re: Possible actuator problem

Post by Tobe »

Did the glitches on the Impala happened when you gave up elevator? Have found if you are running to big throws/and not follow the recommended set up the actuator will occasionally cycle when up elevator is given. Just to he sure we are talking about glitches and not occasional cycling at inputs.
The issue that trigger the glitches is well known, it's the Eddy currents created when the motor reverses with the known consequences which also heat up the motor at high rates and that's what the additional resistor is suppose to suppress, this was also an issue with the original Rands and why they had a 100 ohm resistor crossover at the motors terminals. As we have doubled the driving voltage it need to at least doubled.

Looking forward to test the new schetch when you are done .

Cheers
Tobe
Cheers,

Tobe
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Mike_K
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Location: Hertfordshire

Re: Possible actuator problem

Post by Mike_K »

Hi Tobe

I should really be calling it a "momentary freeze", not a glitch. The actuator motor stops for a fraction of a second, maybe 0.5 to 1 seconds before it starts again, it's really easy to hear the difference from when the actuator is galloping away. And I have tried both the actuators I've had from you, but with the same "momentary freeze".

And it's definitely not the motor over-running and doing a complete cycle. I have managed that during testing, but the motor keeps running when that happens, it's completely different.

But we need to keep things in perspective, the "momentary freeze" (as I'm experiencing it) is short enough that I would still fly with it, as I tried at the recent Ivinghoe Nostalgia Day. And I didn't mention it earlier as I assumed that I was doing something wrong. But when I heard others were experiencing the same, I decided to see if I could solve it, to give us all greater confidence. It isn't a major problem for me and as the fix appears easy (an extra wire and a firmware update), then for me it's worth doing.

Cheers

Mike

PS I'll see if I can rig up my camera on a tripod and video it tomorrow.
AllenD
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Joined: 21 Mar 2019, 10:32

Re: Possible actuator problem

Post by AllenD »

I agree with Mike, the problem is that the actuator will simply freeze, randomly, for an instant. This morning I plugged in the receiver battery on my Fidget and let it run for a while, trying to watch the actuator the whole time. After a couple of minutes the actuator stopped, but I was looking at the elevator at that minute. Less than a minute later, it stopped again. This time I was looking at the actuator, it stopped with full right rudder and up elevator applied, just for an instant, then went back to working normally. I let it run for at least five or six minutes longer, with no more stops. I am also not afraid to fly the Fidget, as most of the stops are not close to the ground and at speed and only last long enough to cause it to stand on a wing tip for an instant, giving plenty of time get it back level. When slowed down for landing, the Fidgets control response also slows down, so the plane doesn't get quite so out of level during the time the actuator stops working, also giving enough time to level the plane before hitting the ground. But, I would sure like to get the actuator to quit suddenly stopping, as for a second it sure raises my heart rate.
Tobe
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Re: Possible actuator problem

Post by Tobe »

A quick note in this matter, after testing done by others and myself on the bench and in flight we have found out that some of the side equipment we use eg. ESC and Rx reacts differently to transient currents from the motor ending for some, in short glitches/momentarily freezing of the actuator. An other issue here is also the load posed on the actuator like linkage and hinges which can cause the same symptoms.
It has to be noticed once more that not all users are affected by this issues and that the chosen side equipment as the proper installation is outside my control.
...but wise of feedback, testing and experimenting I would recommend to add to the motor a "filter" eg. a 200R 1w resistor across the motor terminals in conjunction with 2 Zenner Diodes 5,6 V back-to-back, see picture (Courtesy of Mike K). This will be standard from now on all GG-Tobe and I would recommended this add on also for those of you running the DIY DigiSpark recoders.
If you are not sure concerning your side equipment impact I would recommend the usage of a separate battery running the actuator as suggested by Phil and I will be happy to add proper connectors to GG-Tobe accordingly on demand.
Attachments
zener_diodes.jpg
Cheers,

Tobe
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drigotti
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Joined: 29 Aug 2018, 12:44
Location: Ohio USA

Re: Possible actuator problem

Post by drigotti »

I'll assume the Zener are 3W?
Dave Rigotti
Tobe
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Re: Possible actuator problem

Post by Tobe »

3 to 5 w should do fine, in my tests I used what I had home and that was 1w.
I have hope to replace the 2 diodes back to back with a Bidirectional TSV Diode but haven't received them yet and need some more testing
Cheers,

Tobe
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Phil_G
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Re: Possible actuator problem

Post by Phil_G »

Tobe wrote: 18 Nov 2019, 06:45... If you are not sure ... I would recommend the usage of a separate battery running the actuator as suggested by Phil and I will be happy to add proper connectors to GG-Tobe accordingly on demand.
...and of course any stand-alone recoders I've supplied I'm happy to modify to a separate battery.
Thanks for taking this up Mike, looking forward to your "10% off" code :D
For existing recoders, I've some 6.8v TVS diodes on order which have a similar effect to two opposed zeners: https://www.ebay.co.uk/itm/10x-P6KE6V8C ... 2670026775
These were the lowest voltage TVS I could find at 6.8v but ideally 'just above supply voltage' would be best, with the low-value resistor in parallel across the brushes:


tvs.jpg


Incidentally, has anyone tried a simple decoupling capacitor across the receiver power rails (like the famous Spektrum "capacitor-on-a-plug"), say at least a few hundred μF ? (I think the Spekky ones are 4700μF)

Cheers
Phil
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Shaun
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Location: West Yorkshire

Re: Possible actuator problem

Post by Shaun »

Just to add my experience in the mix to date.

I've had no glitches that I've been aware of using the original Re-coder on my Tobe Rands and I've had lots of flights over the last 3 years or so.
My standard set up now uses the Bec on the ESC
(Turnigy Plush), no separate battery, original spektrum Rx. However, I have had wobbles when I tried a 6 volt output from the Bec and / or had too much travel by winding up the ATV setting on the tx ; both caused cycling that I initially thought was a glitch. Additionally when I replaced my Spekky Rx with a FrSky one I did get a signal loss situation with the aircraft going into failsafe when flying a distance away and low, but I subsequently found that one of the antenna had moved and was touching the actuator motor. Moved antenna and all was fine again.

I've concluded that issues are possible but it would appear to be dependant on the gear and installation, especially bind free linkages and hinges.. I only use stitched ones for all my GG models. Oh, and aerial routing 😳

I may have had the odd glitch but I've never been aware of it in flight to date.

However being a big believer in the saying "never say never" I will be adding the suggested zener / TVS, resistor mod.

If any one flew original GG set ups then you'll remember how difficulty it was to get consistent,
repeatable flights....especially when using a relay rx
This modern GG emulation is brilliant.

Cheers,

Shaun.
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