Subject:
|
Re: High current speed controllers
|
Newsgroups:
|
lugnet.robotics.handyboard
|
Date:
|
Mon, 8 Dec 1997 18:17:48 GMT
|
Original-From:
|
Chuck McManis <cmcmanis@freegate.#AntiSpam#com>
|
Reply-To:
|
CMCMANIS@FREEGATE.ihatespamCOM
|
Viewed:
|
858 times
|
| |
|
|
I designed a high-current H-bridge to use with my Handyboard
(the specs are at
http://www.professionals.com/~cmcmanis/h-bridge/h-bridge.html)
Using heat sinks on the MOSFETs the bridge can control 50A. (You
can substitute fets to get more power). The known problems with
this design so far are that the power to the charge pump is the
same as the power to the motors (the bridge is optically isolated
from the digital side) and when the batteries voltage drops below
the minimum voltage of the charge pump the FETs are sent into a
linear state and can toast. The work around is to lift pin 8 of
the 622 and use a separate battery on the charge pump. I'm
looking for some more clever solutions but a clean one hasn't
presented itself yet.
I put together a bunch of kits for the Homebrew Robotics Club (no
there aren't any left sorry) and we've built a bunch of these. So
far the only problem has been the low battery voltage one. I'll
put the gerber files up on the web page so that you can send them
to APC if you want to build them yourself. The longest lead time
part is the MAX622. Cost per board will be in the neighborhood of
$35 depending on what it costs you to get the boards done and how
many you make.
As for the question of analog vs digital. Its a question of
efficiency and what you can change. Straight analog power
amplifiers seems to be fairly inefficient (generate lots of heat)
and that translates into shorter battery life. Generally on a
robot that would be enough to rule it out right there. Digital
control on the other hand depends on the ability to tune one's
control signal to the resulting motor. I've found with my bridges
that I can really effect the "smoothness" of the PWM output by
tuning the PWM frequency. I need to understand this better but
suffice it to say, when its wrong the result is that a small bit
of "on" gets you 100% of motor activation.
--Chuck
|
|
Message has 1 Reply:
Message is in Reply To:
 | | High current speed controllers
|
| Hello, I was wondering if anyone could recommend a speed controller circuit for controlling a 12VDC motor which could draw up to 25A. I'd like to use the Handy Board to control its speed. Cost is not a big concern but compactness is. I would (...) (27 years ago, 6-Dec-97, to lugnet.robotics.handyboard)
|
6 Messages in This Thread:
 
- Entire Thread on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
This Message and its Replies on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
|
|
|
|
