Solenoid valves

francis_L_H

I am doing a project to make an automated liquor/soda mixer with the BS2.· I am not for sure how to up the 5V on my BS2 to 12V for the valve.· I know I can use relays, but I am not for sure what I am buying.· I have an op-amp, but I have no idea how to wire the circuit.· If anyone knows how to power the solenoid valves I would appreciate the help.

Martin Hebel

Hi Francis,
The easiest means is probably to use a power transistor to drive the relay.· The diode will protect the transistor when the solenoids field collapses.·· A realy, unless solid state, won't help a lot since it it would probably need a transistor driver also.
if you need to control multiple solenoids you may look at the ULN2003, which is a high current driver - currrent sink, connect like the colllector on the transistor.

See attached image.

-Martin




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Martin Hebel
Southern Illinois University Carbondale - Electronic Systems Technologies

Personal Links with plenty of BASIC Stamp info
StampPlot - Graphical Data Acquisition and Control

francis_L_H

Thanks for the help.· I should have stated the first time that I am using a BS2 board of education.· It is rated at 5V, so to control a 12VDC or 24VDC solenoid I will need a external power source.· So won't I need a transistor and a relay so I can trigger the relay with the 5V out from the Stamp to switch the relays to power the 3 solenoids with 12VDC?·

Francis
KUME·

Jon Williams

No, you don't want to connect a relay (unless it's a low-current SSR) to the BASIC Stamp. Open the graphic in the post above -- that will show you what you need to control your solenoid. Yes, you will need an external 12 or 24 volts source, and you need to connect ground of that source to Vss on the BoE.

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Jon Williams
Applications Engineer, Parallax

Martin Hebel

THe 12V doesn't have to come from the BoE as long as both have common grounds. If you need isolated grounds, then you'll need to use an opto-isolator. Ask again if this is needed.

You really gain nothing by putting a relay between the transistor and Solenoid. And in my post earlier I used relat (or realy...) mistakenly when I meant Solenoid... that same thing as far as control goes.

Jon covered most of this, just thought I'd re-emphasize.
-Martin

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Martin Hebel
Southern Illinois University Carbondale - Electronic Systems Technologies

Personal Links with plenty of BASIC Stamp info
StampPlot - Graphical Data Acquisition and Control