[TriEmbed] Circuit Help

Rick nm3g at triad.rr.com
Fri Dec 4 18:15:08 CST 2015

Good evening Brian,

I think you'll find an H-Bridge to be the best solution from an 
availability standpoint (used to drive stepper motors and DC 
brushed/brushless motors), the inherent lockout design (keeps you from 
shorting your supply bus), and the isolation necessary between your 12 
volt power supply and your controller circuitry. Oh, did I mention the 
good H-Bridges limit current?

Simple to implement, one I/O line to turn on, second I/O line to turn off.

Not sure if anyone has made an H-Bridge interface board specifically for 
the Raspberry PI ... but I've seen H-Bridge boards for arduino at Radio 
Shack, as well as the usual internet sources. Solder a couple of I/O 
lines and a ground, and you are in business. Hot glue makes wonderful 
mounting hardware, by the way.

You can build your own H-Bridge if you need more current, just include 
an interlock circuit that pulls the opposite bridge device inputs to 
ground when you enable ... add some time delay to keep from blowing 
transistors off the board (no, you may NOT ask me how I know about 
this!). :)

Hope this helps.



> On Fri, Dec 4, 2015 at 12:51 PM, Grawburg via TriEmbed 
> <triembed at triembed.org <mailto:triembed at triembed.org>> wrote:
>     I have a quarter-turn ball valve with a 12V actuator [HSH-Flo 1/2"
>     DN15 12VDC CR-05 FNPT SS304 Position Feedback Motorized Electric
>     Ball Valve.]  I'm using opto-isolated relay activated by a
>     Raspberry Pi but can only control one direction because the valve
>     reverses direction by flipping the leads. If I was doing it
>     mechanically I would have a double pole triple throw rotary
>     switch. I cannot find a suitable opto-isolated relay that is
>     2P3T...at least one that doesn't cost a fortune. Any suggestions
>     to help me think this through would be welcomed.
>     Thanks,
>     Brian Grawburg

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