Using car wiper motors
I'm new to BEAM robotics ...
I've selected to make a 4 legged walker
for my junior level Mechanical Engg year project
But the professor wants me to use big wiper
motors(12V DC) salvaged from cars.
I've made power transistor based H-bridge circuits ...
It works ..
My question is that can I use those with the
Nv nets ?
any links and help is highly appreciable.
Thnx in advance
Welcome. I don’t know of any reason that you couldn’t, I’ve done very nearly the same thing, albeit with smaller (and more efficient) motors. You have a couple of choices in the way you do things you could use the same power supply for both the motors and the Nv nets. That way you’d have to use logic chips that can handle 12v such as the 4000 series. That would be the simplest way but it has a couple of disadvantages. First you have higher voltages to contend with through the Nv net than normal (obviously) that means that you have to make sure the capacitors can handle the voltage, and you’ll have higher power dissipation through the whole thing. The other thing to keep in mind is that 4000 series chips don’t have very sink/source capability so they might not be able to drive some H-Bridges On the plus side it is the simplest way to do it, and if your H-bridges are compatible it should work just fine.
The other way to do it, slightly less BEAM perhaps (more complicated, doing the same task, but safer) would be to run the Nv net at a lower voltage than the motors. In between you’d need some form of level shifting circuit that would do the conversion between the 5v (say) logic and the 12v motor drive. I’ve got a bot that I’m working on that has a level shifting circuit that goes the other way (12v to 5v) and after a little tweaking I was able to do it with a couple resistors and a NPN transistor for each line. There’s probably a better way but it works fine for my purposes. The main disadvantages to doing it this way are the increased complexity (and thus cost) and the fact that you will get almost zero feedback from the motors. You already are sacrificing feedback using H-Bridges though, so it’s nothing you could avoid entirely.
There could be something else I’m not thinking of but don’t see any reason you couldn’t complete the project with a standard Nv net, and some creative interfacing circuitry. Let us know how things turn out, and just ask if there’s anything else.
Martin Jay McKee
- Can you use a high power h-bridge and wiper motors to make a (2
motor?) 4 legged walker using Nv nets? Depends on a few details.
What is the logic control voltage of your bridge circuit? Does it
require active high or low signals. Are there illegal input states?
It is possible to use wiper motors but risky because these motors
have powerful torque and can do some real damage. With a 12V supply
and a locked or stalled leg, the motor current is 25A-30A. Is your h-
bridge capable of handling this? You will also need end of travel
switches and/or position feedback. Yes, a simple Nv net can be used
but some extra precautions are needed. Any ideas how to go about this
(hint - virtual limit switch)? Consider using 6V to reduce the risk
and make the interfacing with HC logic simpler.
--- In email@example.com, "auvibuet" <auvibuet@y...> wrote:
> I'm new to BEAM robotics ...
> I've selected to make a 4 legged walker
> for my junior level Mechanical Engg year project
> But the professor wants me to use big wiper
> motors(12V DC) salvaged from cars.
> I've made power transistor based H-bridge circuits ...
> It works ..
> My question is that can I use those with the
> Nv nets ?
> any links and help is highly appreciable.
> Thnx in advance
- I think Vishy had built a walker with those motors. Look on
Solarbotics.net. He had a site there with some information.
>I'm new to BEAM robotics ...
>I've selected to make a 4 legged walker
>for my junior level Mechanical Engg year project
>But the professor wants me to use big wiper
>motors(12V DC) salvaged from cars.
>I've made power transistor based H-bridge circuits ...
>It works ..
>My question is that can I use those with the
>Nv nets ?
>any links and help is highly appreciable.
>Thnx in advance
>Yahoo! Groups Links
- Could and ABcore be used/modified to do this? Perhaps that's a way around
having to supply the huge current demands continually. Just a thought.