Topic: A simple DIY servo exerciser for soaktesting servos

I've uploaded an article [here] which shows how to make a really simple servo exerciser for soak-testing new servos or checking old ones. Since theres no discussion with articles, so I thought I'd post a thread in case there are any questions.
As usual I'll do the pics at cost, that is £1.36 for the chip, .61p for post (large letter) and .35p for the jiffy, call it £2.50 all in.
You'll need to provide your own servo extension lead.
Use paypal please, to Email philg@talk21.com and select 'Personal gift' to avoid charges. Ta.

Cheers
Phil

its a really good idea Phil and really simple, so many times ive buried a wing servo in and then to find its faulty, especially with the odd cheap servo that dosent work after 5 min 

Darren

Phil, I've put a comment on GC, but for the majority of us who use commercial battery packs, you need two sockets from a Y lead, not an extension, or you'll have nowhere to plug a battery in!
Works a treat btw.
Bob

Thinking about it, instead of cutting the sockets off, why didn't I just leave the standard Y lead intact and cut the plug off,  there'd only have been one set of wires to solder to the chip!

Another thought that's come to me as a single servo buzzes away, how many servos could the pic drive?  Most of my models run between three and five servos, could the pic drive a complete batch of five?

you need two sockets from a Y lead, not an extension, or you'll have nowhere to plug a battery in!
Works a treat btw.
Bob

Thinking about it, instead of cutting the sockets off, why didn't I just leave the standard Y lead intact and cut the plug off,  there'd only have been one set of wires to solder to the chip!

Another thought that's come to me as a single servo buzzes away, how many servos could the pic drive?  Most of my models run between three and five servos, could the pic drive a complete batch of five?

I'm assuming the cap is just for smoothing, so is not critical regarding size?
 ... I slapped in a random poly the same size as the chip and it worked.  The markings had worn off the capacitor but it must be in the right ballpark as the servo is buzzing away as I type.
I used the two tails from a Y lead as all my RX batteries are fitted with plugs, not sockets.  I removed the signal lead from the power socket so I can identify between them. Thanks again, Bob

Bob yes you're right but what I used was a "male to male" in the battery socket, just 3 pins snipped off a header, so the battery socket can be a plug or a socket. I figured more people would plug it into a rx/bec than would plug it into a battery, but the adapter idea gives both. Or, you could wire it to a battery box & just put 4 loose nimhs in it.
The cap is purely for decoupling, nothing to do with timing or anything, so as you say its not at all critical. It should drive 5 servos ok, the pic can sink/source 25ma to the signal inputs.
Anyway glad you got it ticking away,
Cheers
Phil

Superb, Phil. Can I suggest the next in this pr4oduct line? I can see a use for a variation on this with the ability to move to commanded centre, full+ and full- positions (perhaps with programmable limits to accomodate the different funtaba/JR/Multiplex interpretations of "100% travel". This would need three inputs, or perhaps a sequenced input on a single button - and the cherry on the cake would be an optional analogue (pot) input to give full servo-test functionality.

I know it's a long wish list, but I've always been one who will aim for the stars to ensure we get the moon...

:0)

PDR

I Know it's fun making them, but this does most of those things and is very inexpensive..
Hobbyking servo tester

It will continuously cycle too..

Hi Phil, been using mine today and it works great, thanks mate.

I Know it's fun making them, but this does most of those things and is very inexpensive..
Hobbyking servo tester

It will continuously cycle too..

your point being?

Sorry peeps, there will be a couple of days delay as I've run out of pic chips... they're on order from RS so I'm guessing tuesday/wednesday - never realized how popular this little thing would be!   It was only last Thursday Simon prompted the whole thing with his duff glued-in aileron servos...
I promise to get them out ASAP,

Pete (pdr), have you seen the Pulstar?  thats the one you see at the beginning of the video.
Its a bit dated, I might update it if theres any interest. EPE no longer list articles >10 years old so I guess its ok to post - see attached.
Cheers
Phil

The LCD doesnt photograph well...




http://www.mccrash-racing.co.uk/pics/pulstar1.jpg
http://www.mccrash-racing.co.uk/pics/pulstar2.jpg
http://www.mccrash-racing.co.uk/pics/pulstar3.jpg
http://www.mccrash-racing.co.uk/pics/pulstar4.jpg

Ok Phil, I'll start the ball rolling. I NEED one of these things, always wanted something like that. Veroboard would be fine for me, just pop it in a suitable Maplin project box.

It would also fullfill another need of mine. When not being used as a servo tester, I'd plug in an old brushed speed controller to adjust the speed of my Dremel drill.

Andrew

Hi guys, Re my post above I apologise if I upset anyone, I was merely trying to point out an alternative.

I used to build a lot of small electronic projects but am increasingly frustrated that there are commercial alternatives available for very little money.

I do really like the simplicity of the original idea here. Keep up the good work.

Hey no probs, each to his own

Chaps the RS package arrived this morning, so I'll be sending the chips out today. We only get one postal collection  per day.
Any more for any more?
Phil

Phil, can you put me down for one, paypal done 

Steve

Steves, Mark (x2), Gerry W & Dave N in the post
ta
Phil

Hi Phil,

Yes please, PayPal done and PM sent 

Cheers
Steve

Phil

Has anyone any experience of running this unit on more than 4.8v.  I was thinking of 2 x A123 cells, which give about 6.6v. Would that let the magic smoke out?

Pete

The pic spec is 6.5v abs max Pete, so fresh off charge at 2 x 3.6v it would be well over.  Once they've settled down to 3.3 it would probably be fine.
I'd use a 4-cell battery pack & some old nimh out of the junk box  or some old rx pack you darent fly again but too good to throw away (we all have them!)  or even 4 Poundland LSD's   (2 per pack)
To use A123s you could mess about with diodes or even an LDO reg but I wouldnt bother.
Cheers
Phil
EDIT:   in fact I have a 2S A123 right here, I'll try it!

Well, I never saw that S3001 move so fast... but no smoke after 20 minutes. I'd guess you're ok
[Here ya go...]

Cheers
Phil

Well, I never saw that S3001 move so fast... but no smoke after 20 minutes. I'd guess you're ok
[Here ya go...]

Might be a little smokier if there was a load on the servos, so I'd still be wary of trying to run directly from the 2-cell setup in an aeroplane!

PDR

Not too sure the servo was that happy, heard some peculiar chirping noises about 40 seconds in.

Can (ary) it be feedback on the pots?
 

heard some peculiar chirping noises about 40 seconds in. Can (ary) it be feedback on the pots?    

Ah, that would be Schnaps... who gets a word in on all my videos...

Phil

Thanks for the comprehensive response, and video.
The digital servos will be run off 2 x  twin A123 2300mah packs (fed by a Smart Fly Power Expander system), so I wanted to check that the tester would be happy with those volts,
The little FU2A fun-fly runs happily on a pair of the smaller A123s, but that only has one hefty servo.

Pete

Quick update, mine arrived today, and after a few minutes work was hooked up and working like a champ.

Thanks Phil 

Steve

PM sent. 

May end up needing more than one yet, depending on replies from mates.

Owens, Tims, Bills & Alasdairs just posted.

Phil

Owens, Tims, Bills & Alasdairs just posted.

Phil

Safely received today Phil - many thanks. A

Owens, Tims, Bills & Alasdairs just posted.

Phil

Owen's has been received. 

And I've built it, working perfectly. 

Nick G's posted
P

Having been accused of being a model flyer and not an aeromodeller, my curiosity got the better of me.

I had bought a PICkit 2 after a recommendation on this forum some time ago, but had not found the time (or ability) to do anything with it except make some LED's flash.

So in the last couple of days, I've bought some 12F675s and knocked up a programming adapter and now two of these servo exercisers. I have to admit, they do a job I didn't know I needed, but I can really see the application now. They could even be used after fitting out a model to check surface centering and slop etc..  Very well done Phil.

Here's my feeble attempts,
1, the programming adapter, with servo lead so I can test it in situ.
2, an exerciser with two headers and no leads - just plug battery and servo in directly.
3, the version intended by Phil.

Now, could I possibly be reinstated as an aeromodeller? what do you think?
Cheers
Chris

Having been accused of being a model flyer and not an aeromodeller...

Aw shucks I feel awful now, that was supposed to be just a tongue-in-cheek metaphor, and I do apoligise... you were absolutely right , a lot of these modules are cheaper to buy than to make, just like ARTFs!

Where a lot of the more elaborate submissions have raised very little interest, this one has gone nuts, probably because its so simple

Now, could I possibly be reinstated as an aeromodeller?

Absolutely Chris!  I stand humbled & corrected!

what do you think?

Anyone who'll have a go at something new is a top gadge in my book
Cheers
Phil

Cheers Phil :-)

Now you've only gone and sparked my interest in PICs again, lets hope I can find the time to get a bit further than last time. (I doubt it in reality, just too many priorities)

Are you OK with me making a few of these for club mates at cost? With appropriate credit to you of course.

One gadget I would really like added, would be an option to keep the servo at an accurate centre. To hold it in place while surfaces are set up etc.

Chris

In the past (OK, way back in the past...) I dabbled a bit with building simple electronic stuff.  Somewhere (probably in my parents' loft!) I have several years worth of Practical Wireless magazines from around the early seventies.  In recent years I've done very little - largely, as mentioned before, because we can now buy, ready made,  the sort of thing we used to build - and probably for less cost too. 

Now, PICs - there's something I've heard of, but never tried myself.  I remember somebody producing some simple PIC-based projects in RCM&E a few years back...  even if I can't remember his name!  Perhaps I ought to have a closer look at these devices...

Are you OK with me making a few of these for club mates at cost?

No problem, thats what its here for!

One gadget I would really like added, would be an option to keep the servo at an accurate centre. To hold it in place while surfaces are set up etc.

You mean just constant 1.5ms pulses to stop the servo being physically pulled off-centre ?

Here ya go, same hardware:

:020000040000FA
:100000008316FF2390003B3085008312F930A00057
:100010000515000000000000A00B092805111A308A
:0C002000A100A00B1128A10B112806283C
:02400E00C43FAD
:00000001FF


Cheers
Phil

Built in under 10 mins, (incl burning the carpet! :' ) and works great. Thanks

Great thanks Phil that code works spot on.

I think I was thinking of a switched option on the original, but I guess a switch might be as expensive as building an extra unit, and would make it more complicated, requiring a circuit board, enclosure etc etc.

Cheers
Chris

Mine also now built and working great - huge thanks to you Phil

Still not sure I need one,but I could not resist, I ordered a PIC from Farnell and programmed it at the weekend and I now have a nice servo exerciser....

Many Thanks

Still not sure I need one, but I could not resist...

It all started with someone over on Giantcod who wanted to test new servos thoroughly before gluing them permanently into his wings... put one together for him that evening, then it occurred that it might be of interest elsewhere so posted it and its gone crazy ever since. I think its just because its such a simple project. If it has rekindled anyones interest in electronics, thats fantastic!

Marks, Dougs (x2) and Julies posted this morning.

Cheers
Phil

Marks, Waynes & Johns posted today
P