go_away

Author Topic: Scooter Motor Controller?  (Read 6290 times)

0 Members and 1 Guest are viewing this topic.

Offline MaltiKTopic starter

  • Robot Overlord
  • ****
  • Posts: 300
  • Helpful? 2
Scooter Motor Controller?
« on: January 25, 2009, 02:38:22 PM »
I recently bought two used Jazzy Wheelchair motors, and I am not willing to spend 200-ish dollars on a suitable motor controller. What I wonder is how to use a scooter motor controller? Has anyone interfaced them before? What was your outcome? Thanks!

EDIT: They can handle a huge load of Amps as well as voltages and are cheaper and more readily available. I am looking for a 24v 30ish Amp driver...
« Last Edit: January 25, 2009, 02:47:43 PM by MaltiK »
Warranty

Offline airman00

  • Contest Winner
  • Supreme Robot
  • ****
  • Posts: 3,653
  • Helpful? 21
  • narobo.com
Re: Scooter Motor Controller?
« Reply #1 on: January 26, 2009, 07:57:30 AM »
If you want cheap ( but no speed control) use automotive relays.
Check out the Roboduino, Arduino-compatible board!


Link: http://curiousinventor.com/kits/roboduino

www.Narobo.com

Offline MaltiKTopic starter

  • Robot Overlord
  • ****
  • Posts: 300
  • Helpful? 2
Re: Scooter Motor Controller?
« Reply #2 on: January 26, 2009, 12:17:51 PM »
If you want cheap ( but no speed control) use automotive relays.

But I want speed control :/
Warranty

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Scooter Motor Controller?
« Reply #3 on: January 26, 2009, 03:09:29 PM »
Hi,

Just PWM a MOSFET that can handle the current.
The key to a cool running MOSFET is to have ample current to switch its gate (like 2..5A).

That is, assuming you would be able to use a scooter regulator, which AFAIK is unidirectional (i.e. no reverse).
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline ArcMan

  • Supreme Robot
  • *****
  • Posts: 519
  • Helpful? 4
  • Mmmm... Plasma
Re: Scooter Motor Controller?
« Reply #4 on: January 26, 2009, 03:47:47 PM »
I built a cheap motor driver using MOSFETs and HIP4081A MOSFET drivers.
I still haven't got it working reliably yet.  I just gave up and bought a Dimension Engineering Sabertooth 2X25 drive (about $130).
If someone tells you it's easy, they're wrong!  Once you get up into the 10A+ range of current, things get difficult.

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Scooter Motor Controller?
« Reply #5 on: January 26, 2009, 05:16:51 PM »
If someone tells you it's easy, they're wrong!  Once you get up into the 10A+ range of current, things get difficult.
Baloney!
You just need to know what parameters are important and then satisfy them.
10A is small potatoes, and 50A+ is still quite attainable for an amateur (as long as they know how to read a datasheet).

If you cannot get yours working, then post a schematic of what you did (preferably reverse engineered from what you actually build, rather than the schematic you started from) and photos of the PCB from both sides.
I assume you did take all precautions against ESD when you mounted the MOSFET!?!
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline ArcMan

  • Supreme Robot
  • *****
  • Posts: 519
  • Helpful? 4
  • Mmmm... Plasma
Re: Scooter Motor Controller?
« Reply #6 on: January 27, 2009, 12:54:52 PM »
I'll post a picture.  I somehow lost the schematic, but I'll reconstruct it.
I've never been able to talk to somebody who REALLY knows what he's doing as far as MOSFET drives goes.  That's probably why I think it's so difficult.
The latest problem I have is that I'm using 15 ohm resistors between the MOSFET driver and the MOSFET gates.  One of them burned up.  It wasn't the first.  Is a gate resistor really needed?  I'm running the PWM at ~20 kHz, so I imagine that resistor is taking a pretty good load.

EDIT: I found the schematic I was working on.  It's almost done, but I haven't added the actual component values yet.



« Last Edit: January 27, 2009, 01:14:19 PM by ArcMan »

Offline MaltiKTopic starter

  • Robot Overlord
  • ****
  • Posts: 300
  • Helpful? 2
Re: Scooter Motor Controller?
« Reply #7 on: January 27, 2009, 01:14:20 PM »
I'll post a picture.  I somehow lost the schematic, but I'll reconstruct it.
I've never been able to talk to somebody who REALLY knows what he's doing as far as MOSFET drives goes.  That's probably why I think it's so difficult.
The latest problem I have is that I'm using 15 ohm resistors between the MOSFET driver and the MOSFET gates.  One of them burned up.  It wasn't the first.  Is a gate resistor really needed?  I'm running the PWM at ~20 kHz, so I imagine that resistor is taking a pretty good load.

EDIT: I found the schematic I was working on.  It's almost done, but I haven't added the actual component values yet.


I didnt know MOSFET's were capable, in general of withstanding 20amps+
Warranty

Offline ArcMan

  • Supreme Robot
  • *****
  • Posts: 519
  • Helpful? 4
  • Mmmm... Plasma
Re: Scooter Motor Controller?
« Reply #8 on: January 27, 2009, 01:40:51 PM »
I'm using Fairchild HRF3205 N-channel MOSFETs, which are rated for 100A (8 mohm RDSon).
My drive can't actually handle that kind of current because of other considerations, like wire size, terminal ratings, etc.
That is want I meant when I said designing a drive of 10+ amps is not easy, even if some folks think that's baloney.  Let me rephrase...  It's not easy for us mere mortals.
« Last Edit: January 27, 2009, 07:08:12 PM by ArcMan »

Offline Admin

  • Administrator
  • Supreme Robot
  • *****
  • Posts: 11,657
  • Helpful? 169
    • Society of Robots
Re: Scooter Motor Controller?
« Reply #9 on: February 07, 2009, 07:58:26 AM »
I'm with arcman on not making handmade motor drivers. They require tons of wiring, and the high voltages/currents mean that a mistake results in a fried circuit. I badly burnt myself on my first attempt . . .

If you make your own, it'll cost you about ~$30 and ~10 hours of your time. But that's only if it works the first time . . .

My time is valuable, I'd rather just get something I know that works.

 


Get Your Ad Here