Re: SSRs, relays, speed controls

["flier" <FLIER-at-sbcglobal.net>]

Ah ha!  Great.  I have six of the D1D40 Crydom SSRs 
on the way but was trying to figure a cheaper 
solution since those things actually sell for 50$ or 
more each.  Using two makes the controller more 
reasonable if someone had to buy the relays 
wholesale.  Plus, I'll have relays on hand for THREE 
tanks now  ;^)

Hey, sign me up for some code when you can.  I 
already have some '876s on the way.  I think I'm 
going to try some of those cheap 40A 12v spdt auto 
security relays first so the PCB won't be necessary 
yet.  At less than $2 a pop I can see how they work 
and go the other route if they crap out.

--- Original Message ---
From: Joe Sommer <anvilus9-at-adelphia.net>
To: tanks-at-rctankcombat.com
Subject: Re: SSRs, relays, speed controls

>
>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
>