From bench to real world...

starion

I finally have my first *paid* project that uses a Basic Stamp! Woohoo! Probably a BS1, but could be a BS2.

The project involves hooking (3) 5VDC IR sensors to the stamp via less than 10 feet of 22/4 wire on each sensor. The sensors have a plus, minus, and Vout that is either high or low.

On the output side, I will be driving a relay that controls a couple of 110VAC solenoids.

Is there anything I should be doing to the circuit (input and/or output) to protect against possible noise, interference, coil kickback?

Chris Savage

Jeff,

·· For starters you won't be able to control the relay directly.· You will need some sort of driver.· Either a MOSFET or a Transistor.· Really depends on the coil voltage/current.· But this driver will need protection against inductive feedback.· This is in the form of a diode.· If you're using a chip like the ULN2803, this is provided, if you connect it properly.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

Guenther Daubach

Jeff,

instead of mechanical relays, you might consider using solid-state relays instead. Fron the input side, they "look" like photo-couplers, i.e. you can drive them directly from BS output pins (with a current-limiting resistor in series). Most SSRs have an integrated zero-crossing detector, i.e. they turn on the load when the AC signal crosses zero, and this avoiding "spikes".

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Greetings from Germany,

G

starion

Yes, since posting this, I dug up some Opto22 solid-state relays in my parts bin, I will be using that to switch the AC side. I think it has a 5V opto input, I should be able to drive that directly, right?

Post Edited (Jeff J.) : 1/4/2006 2:32:55 PM GMT