Chris Bott - Moderator Posted November 24, 2018 Share Posted November 24, 2018 In case anyone was wondering "what's the point" (It's a very good question), here's a video of what the servo exerciser electronics project in the Dec mag does. I find it most useful for checking the centring of servos, or even control surfaces. For anyone extremely picky you can just detect a centring difference in the video, depending on which direction the servo is coming from. Quote Link to comment Share on other sites More sharing options...
Phil Green Posted November 24, 2018 Share Posted November 24, 2018 From 2010. Skip to 7m44s, the first 7 minutes is the build Edited By Phil Green on 24/11/2018 13:10:55 Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted November 24, 2018 Author Share Posted November 24, 2018 I thought you might recognise it Phil. You even get a mention in the article. Much as I tried to come up with something original, no sequence of events seemed better than than the one you had come up with. Quote Link to comment Share on other sites More sharing options...
Phil Green Posted November 24, 2018 Share Posted November 24, 2018 Hey no probs Chris , they are very handy especially with cheap servos. Shortly after the video I added an end-to-end sweep with increasing speed, faster & faster until the servo cant keep up. The idea is that with alternate and equal left and right commands, even if the servo cant keep up, it should stay central. Some wander off neutral, indicating a speed imbalance between the two directions. Cheers Phil Edited By Phil Green on 24/11/2018 13:16:19 Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted November 24, 2018 Author Share Posted November 24, 2018 Blimey - as usual you're way ahead of me. Maybe folk can build one and try to incorporate your ideas themselves, or maybe with the help of this thread. Quote Link to comment Share on other sites More sharing options...
Phil Green Posted November 26, 2018 Share Posted November 26, 2018 Did you see my background servo driver for Arduino Chris, makes anything like this a piece of cake **LINK** Edited By Phil Green on 26/11/2018 18:12:02 Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted November 27, 2018 Author Share Posted November 27, 2018 Hi Phil.Sorry for slow reply, a bad back is suddenly taking most of my concentration.No I hadn't seen that. I won't pretend to understand anything of how it works but it does look extremely useful to just cut, paste and use. I assume we'd just make OFR1B = whatever we want the servo to do? (x2).Edited By Chris Bott - Moderator on 27/11/2018 10:25:46 Quote Link to comment Share on other sites More sharing options...
Alfred Vink Posted January 29, 2019 Share Posted January 29, 2019 Hi Chris, Just read the article and was wondering why you decided to power the servos through the RAW pin. Wouldn’t it make more sense to use Vcc? The Arduino can take up to 12V as input, I don’t think all servos would like that. Looking forward to see what else we can do with the arduino. Quote Link to comment Share on other sites More sharing options...
Mike Blandford Posted January 29, 2019 Share Posted January 29, 2019 The regulator on an Arduino Pro Mini can supply up to a total of 150mA. A servo will very likely consume several times that amount when operating. In addition, the regulator has a maximum power dissipation of 450mW at an ambient temperature of 25 degrees C. If you put 12V on the raw input, then, for a 5V Arduino, the regulator will have 7 volts across it. With about 64mA flowing, you will reach the 450mW dissipation limit. Mike Quote Link to comment Share on other sites More sharing options...
Former Member Posted January 30, 2019 Share Posted January 30, 2019 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Phil Green Posted January 30, 2019 Share Posted January 30, 2019 Hi, yes they're clipped but with enough left to attach the power wires, see photos. However, I'd suggest Chris's Arduino variant for a new project, then you could amend it to suit your exact needs. Cheers Phil Quote Link to comment Share on other sites More sharing options...
Alfred Vink Posted January 30, 2019 Share Posted January 30, 2019 Thanks for the clarification Mike, makes sense to me now. Quote Link to comment Share on other sites More sharing options...
SIMON CRAGG Posted January 30, 2019 Share Posted January 30, 2019 I was talking to Motion RC the other day about servo testing. They strongly recommended that all the servos on their models be cycled for at least six minutes, to establish if they get hot. I had one on my Freewing Hawk that was warm to the touch, which they replaced without question. I think this procedure is a "must" these days, when models come with servos of unknown quality etc. I certainly have adopted it as "standard" procedure. Potentially could save a model at the very least!. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted January 30, 2019 Share Posted January 30, 2019 I once had some brand new Bluebird BM621servos on test that got so warm that the leads melted! Edited By Bob Cotsford on 30/01/2019 11:50:24 Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted January 30, 2019 Author Share Posted January 30, 2019 Posted by Alfred Vink on 29/01/2019 17:32:50: Hi Chris, Just read the article and was wondering why you decided to power the servos through the RAW pin. Wouldn’t it make more sense to use Vcc? The Arduino can take up to 12V as input, I don’t think all servos would like that. Looking forward to see what else we can do with the arduino. Alfred, Mike's answer explains why nice and clearly. Thanks Mike. The servo is therefore powered directly by the battery while the voltage regulator on the Arduino drops the voltage to 3.3v for the processor . One thing to note is that this means that the servo can have a supply voltage anywhere up to its limit, while the position pulses coming from the tester will always be only 3.3v. This can be an issue for some servos but is representative of exactly what happens with most receivers. Quote Link to comment Share on other sites More sharing options...
Former Member Posted January 30, 2019 Share Posted January 30, 2019 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted January 31, 2019 Author Share Posted January 31, 2019 Supertigrefan there's nothing on line, unless you're a subscriber and can look at Decembers RCM&E. If it's your first electronics project then you probably need the whole article but if you're determined enough then I'm sure we can help here. The required items are: Arduino Pro-Mini 3.3V 8Mhz £3.11 (bitsbox.co.uk M071) USB – FTDI Program uploader £3.18 (bitsbox.co.uk M070) USB cable – Mini USB. 3 Servo sockets on leads. (Make your own or cut them off servo extensions/ Y leads) The Adruino sketch – Downloadable using **LINK** PC With Arduino IDE software – Free download **LINK** In essence you'd need to follow these steps:- install the Arduino IDE software on a PC. Use the IDE software to open the sketch (program). Set the software up to suit the type of arduino you're programming and the right PC com port etc. Connect everything up, with the programmer set to 3.3v Upload the sketch from the PC to the Arduino board. Here's some pictures to help illustrate. Wiring diagram:- Finished project :- Uploading from PC to Arduino:- A couple of different programmers:- A couple of different Arduino Pro Minis Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted January 31, 2019 Author Share Posted January 31, 2019 PS - This would work just as well on any type of Arduino. For example an Arduino nano Pro, which has a built in USB port. That would mean no separate programmer would be required. Quote Link to comment Share on other sites More sharing options...
Kevin Fairgrieve Posted January 31, 2019 Share Posted January 31, 2019 Any idea Chris, when the follow up telemetry article will be hitting the magazine? Thanks. Kev Quote Link to comment Share on other sites More sharing options...
Former Member Posted January 31, 2019 Share Posted January 31, 2019 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Nigel R Posted January 31, 2019 Share Posted January 31, 2019 Just looked at the Arduino - these things are really simple aren't they? Country mile ahead of previous gen PIC hardware for cost and usability. Maybe a follow on project to do a servo slow / servo reverser / door sequencer? As you've covered servo output (well, two actually - centre, plus exerciser), adding an RX input would be a nice step. Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted January 31, 2019 Author Share Posted January 31, 2019 Posted by Kevin Fairgrieve on 31/01/2019 14:47:27: Any idea Chris, when the follow up telemetry article will be hitting the magazine? Hi Kev The intention was for it to be a two parter in consecutive issues but publishing constraints meant that wasn't possible. (Not that I understand these thigs). Graham is trying to squeeze it into the March issue but it's more likely to be in the April one. That one is more a "this is what I've been doing" piece rather than a straight construction article. There are many ways to build it and many telemetry parameters for folk to choose from. I'm sure you'll have fun having a go and we can expand on it in a thread here. I know I have a lot to learn about these things. Quote Link to comment Share on other sites More sharing options...
Kevin Fairgrieve Posted January 31, 2019 Share Posted January 31, 2019 Thanks Chris. Looking forward to it. Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted January 31, 2019 Author Share Posted January 31, 2019 Posted by Nigel R on 31/01/2019 15:29:50: Just looked at the Arduino - these things are really simple aren't they? Country mile ahead of previous gen PIC hardware for cost and usability. Maybe a follow on project to do a servo slow / servo reverser / door sequencer? As you've covered servo output (well, two actually - centre, plus exerciser), adding an RX input would be a nice step. Nigel those are some nice ideas. I'm not sure I have time to look into them, but there are folk here who are far more knowledgeable than me. I'd be as pleased as punch if someone else put their hand up to write (or help me with) a follow up. Or just as helpful, simply post some "how to" ideas here? Quote Link to comment Share on other sites More sharing options...
Mike Blandford Posted February 2, 2019 Share Posted February 2, 2019 I've got most of the "building blocks", so I'll see if I can knock something together. For things like a servo reverser, I usually use all my own code, no Arduino library code, so there are no "surprises" caused by code I don't know, for certain, what it is doing! The downside is the code may be less clear what it is doing. Mike Quote Link to comment Share on other sites More sharing options...
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