da mad maori

some h bridge circuits yes and some circuits no lol

analogue servos are usually transistor driven so both sides of the bridge are open at center..... if you make an external h bridge from mosfets, then all mosfets will open... making a loud POP and release that mysterious smoke lol

then again some circuits have found away around them

im testing this one and so far so good

http://www.cadvision.com/blanchas/he.../h-bridge2.gif

and thats using an analouge servo...


heres a vid of some chap who is using the same circuit

http://www.youtube.com/watch?v=FWJL1...layer_embedded

krakkah

Cheers thanks!

Dirty_Vinylpusher

Is that Syntax from Ozlargescale?



And who is the guy in Australia he's building 10 boards for?!??!!? [sm=50_50.gif]

da mad maori

LOL i just saw that now...
hopefully he will be finished soon my home made board is falling apart lol

seesoe

hello, thank you for trhe info Maori

i consulted a friend that works for general electric who asked a friend to explain the schematic to him, heres what he emailed me
another friend suggested j1 and j2 are normal switches to maybe flip the values on the table in the schematic, i guess for polarity.

i put in an order for double parts, im going to build 2 of these on one board, its for a much bigger project

thanks again, will certainly report back and give credit
cheers
seesoe

da mad maori

good luck man..
remember, pics pics and more pics

seesoe

just an interesting link, thought id share
also check out the rest of the site, he has bigger  open source h bridges with info on how to make them.

http://www.rediculouslygoodlooking.c...lawnmower.html

cheers
seesoe

da mad maori

this way looks fairly simply... its only 3-4amps but that might be ok....

its a bit hard to read the english translation but ya get the jist of it

http://www.quickest-owl.com/tutorial/giant%20servo.pdf

da mad maori

time to kick this into life again

getting a couple of these
http://www.pololu.com/catalog/product/1393

they "should" be hook it up and go circuits!!!!!

although its $99us, it should be a crap load more powerfull than a Tonegawa.. and with 12amp cont and 30peak, its more than enough

OR

its baby sister
http://www.pololu.com/catalog/product/1392

they appear to be the same type of board but only capable of 3amps.....( a wiper motor will proably be more than this
however with a simple external Hbridge employing 4 mosfets (maybe $3 each) on the output should raise its power capabilities to what ever mosfets you use...
being alot cheaper it may work

if anyone can see a reason why these wont work PLEASE inform us before i folk out $250us on these


i will also try working on a 6volt servo using a 14.4volt cordless drill. (they are quiet powerfull when you hook up 6 volt direct to the motor)

stay tuned but as always, please dont hold ya breath lol

Dirty_Vinylpusher

What happened to the boards that swedish bloke was making for you?

Xirus

I am still interested in building one of these. I'm a mechanical guru, I feel like a complete dummy when it comes to electronics. I it would be nice to have something like this for my 1/4 scale RC tank

[link=http://rckingtiger.weebly.com/]http://rckingtiger.weebly.com/[/link]

I'm so close to giving up and going with a different system. My main advantage is that I absolutely dont need anything that makes very fine proportional movement. Since the steering is controlled by braking either side of a differential I need a simple on/off circuit. To avoid over stressing the wiper motor when it reaches the point where it has applied full brakes to said side. I am thinking of using a NO/NC switch so instead of the motor trying to keep turning, the circuit will kinda bounce between on/off/on/off/on This will still keep the brakes locked and when I release the steering a spring will slowly return the arm on the wiper motor to a neutral position. I hope everyone understands what I'm talking about.

Anyway I'm still expecting to fry a wiper motor every now and then. But since these come from a car that is a dime a dozen at the wreckers I'm not so worried about it.

da mad maori

havent heard boo from him!!!!!

so oh well back to the drawing board

da mad maori

another board

http://www.robotpower.com/products/simple-h_info.html

25amps!!!!!!!!

however this board will need a hacked servo to provide feedback...

Dirty_Vinylpusher

25 amps, jesus that should be enough.
Surely.

da mad maori

well thanks to the help of a friend, we finally got the wiper motor servo going.... and going well i might add

we used this board

http://www.pololu.com/catalog/product/1392

which only handles 3 amps... so we built and added a simple hbridge costing around about $7 on the output.. now it can handle 20 odd amps
board costs $50us,

there is a board that handles 12 amps but its $100..... so a $50 board with a $7 part to handle 2x what the $100 board can do...... makes sense i think

how ever..... the boards need to be programed (set up rather) via a pc program downloadable for free.... so if ya not computer programing savy, then ya probably better off getting a programmer to do it... apparently it was quite simple though so i guess most programmers could do it

heres a vid

http://s9.photobucket.com/albums/a60...eringservo.mp4

ill go into more detail about hooking it up later...

plus ive been working on a 6volt system that is far more simple ....not as accurate but still strong...

Dirty_Vinylpusher

So with a 6V system would you still need the H-bridge or do you just power it straight in to the servo?

da mad maori

still need an Hbridge but theyre simple

valman

Hi guys ,I'm new to this forum but I know of a servo motor source that may be of intrest for mid to large scale projects. Yamaha, on some of their Two stroke motorcycles in the mid 80's to 90's used servo motors to drive the powervalves in the engine via pull pull cable setup. they are a proper striaght gear multiple reduction unit, and quite sizeable (approx. 4 inches ) with an inbuilt 7.5k ohm feed back pot. there are no electronics in the unit, just a 5 wire connector coming out of it , 3 for the pot and 2 to the motor. I think there is a seperate control box under the seat that would contain the H bridge which interfaces to the ignition box so the powervalves rise with revs. Being that it is yamaha and designed to withstand 2 stroke motorcycle use it would be a high quality unit, that being said the price of a new one would probably kill you, maybe from a m/cycle wrecker though ? Anyway the bikes in question that I know used them are : RZ250 and 350, WR 200, DT 200 and DT 230. The RZ ones may be bigger as they drive powervalves in 2 cylinders ( have an RZ I haven't actually seen the other ones, just know they exist ). They would be great for rudder control in large scale planes or boats as they are already set up for cable control. Anyway I hope this info may be helpful to someone. I have a very large scale project going on at the moment, setting up a manual gearbox racecar for a kid without legs to race speedway ! lol Need servos on the clutch and gearbox. Now theres an intresting challenge.Watching your developments with intrest. Good luck.

valman

Just a quick note, another 2 good places for electronics and componentry in Aust. are RS electronics (RadioSpares, they are worldwide, out of UK I think) and WES Components. (Wagner Electronic Services, out of Sydney). I deal with WES regularly, they have heaps of components, and cheap but no data, you have to know what you want.

vugt47

so do you just take the power goin to the motor in the servo, and reroute it to the wiper motor?

Dirty_Vinylpusher

Not quite as simple as that.
(wish it was)

You've gotta build a so called H-Bridge to go between the original servo and the wiper motor to handle the power of 12V.






I'm slowly getting the hang of what that all means but haven't attempted making one yet.

Bong-Master

Glad i stumbleduponthis post will be doing this very soon
I this still a work in progress ? with success ?

nick_75au

Ive been researching the same thing, I had a circuit working well using an Oatly Electronics kit which is no longer made unfortunatly,
I got everything working using some power seat motors, they even had the pot intergrated with the motor so no messy extra arms to drive the pot, only thing is the final test I reverse polaritied....... and [&o] the circuit

Vantec now make a plug and play solution now for $79.95 US

http://www.vantec.com/servocat.html

Worth a shot for those not electronically inclined

Nick

Bong-Master

Nice 1 Nick 

mike_humphreys

Hi Guys, I've read a fair chunck of this thread - yes, even the negative stuff. A couple of things, first of all I'm a racer that uses shop bought stuff so I'd probably never need to make anything electrical other than a loom.

You servo build....

What sort of car are you using this in?

I'm assuming it's for the steering, do you need so much torque from a wiper motor and will the advantage of this home build balance out with the heavy battery you'll have to use to power it?

Have considered using an electric window motor as most of them are smaller?

I can't see any of the videos or some of the photos as I'm at work.