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From: Joe Sommer <anvilus9-at-adelphia.net>
Subject: Re: SSRs, relays, speed controls
Date: Wed, 03 Mar 2004 19:22:46 -0500
Reply-To: tanks-at-rctankcombat.com


Ted,

At 05:09 PM 3/3/2004 -0500, you wrote:
>To keep costs down (given that the applicable
>ucontroller programming would have to be done),
>couldn't one implement full two motor reversable
>speed control using only two SSRs and four regular
>SPDT relays?  Use the SSRs to provide the high
>current PWM and the SPDT relays to do the H-bridge
>switching?  Specifically, use a PIC 16F876 to mix 4
>outputs driving the relay switching and the two PWM
>modules driving the SSRs...

Preliminary coding for this is done except for
exact pin assignments.  I already merged
the code for my full bridge SSR with the code for
Steve Tyng's relay driver board.  The code fits easily
in the 876.

The board will essentially look like the Dual Motor Relay
Mixer shown at   www.anvilus.com  but will require a little
more PCB area for the 876 versus the 628 CPU, and
for extra connecters.

7 or 8 position power connecter
left B+, left B-, left forward, left reverse
right B+, right B-, right forward, right reverse
(motors can share the same B-)

3 or 4 position TTL connecter for PWM output
left PWM, left GND
right PWM, right GND
(outputs can share same GND connecter)

2 position connecter for 12 VDC relay coil power

Each motor will require its own B+ connection.
If you simply wish to use full speed forward/off/reverse,
you will connect the battery directly to the B+.
If you wish to use PWM, you will connect the
battery to the top side of the SSR and connect
the low side of the SSR to B+.

I can send a draft of the PCB layout if you wish.
It has four onboard SPDT relays.

Joe



**********************************************
Joe Sommer
2378 Nantucket Circle, State College, PA 16803
814.234.4773     anvilus9-at-adelphia.net
http://www.anvilus.com