Relay Problem

[LyleCaldwell]

I put together this relay circuit:



And I can't get the relay to flip.  I've measured the voltage, and when nothing is bridging J2, there is no voltage across the relay/D2.  When J2 is bridged then there is 4.9v across the relay/D2.  So the transistor is switching correctly.  I chose a EA2-5SNJ relay : http://www.worldproducts.com/pdfs/ea2.pdf and according to the data sheet this should be flipping the relay.  I've tried both momentary and latching signals.  Yes, I'm sure the relay is oriented correctly.

So am I overlooking something stupidly simple?

[LyleCaldwell]

I've tried the relay in both polarities, btw, and I know the relay works, because it flips when you reverse the polarity (pins 2+3 connected in one orientation, pins 3+4 connected in the other).

[LyleCaldwell]

Ah, damn, I ordered a latching relay by mistake.  One little difference in the part number.  Anyway, if anyone wants to use this, so long as you use a EA2-5NJ instead of a EA2-5SNJ it works fine.

[Peter Snowberg]

..... and I know the relay works, because it flips when you reverse the polarity (pins 2+3 connected in one orientation, pins 3+4 connected in the other).

It's a latching relay? The part number EA2-5NJ (as shown on the schematic) is a non-latching and should work fine. An EA2-5SNJ requires the coil polarity to be flipped to operate and will not work with the schematic above. If you look in the Digital&DSP area, Transmogrifox has a driver that will work for latching single coil relays. Here's his site: http://www.geocities.com/transmogrifox/relay

Look at the second schematic in the first PDF for a driver that will work with your relays. Remove Q1 on your diagram and connect the old base wire to the input of an inverter. Connect the output of the inverter to one side of the coil, connect the other side of the coil to ground via a good sized electrolytic cap (anything from 4.7uF to 47uF should be fine), remove the diode across the coil, and there you have it.

For completeness, the diode across the coil should be replaced with a pair of 4.6V zeners wired back-to-back in series.

[Peter Snowberg]

 

You figured it out as I was making the reply.

[LyleCaldwell]

Still very much appreciated, Peter!

You know how Mouser has those clickable links for parts on their PDFs?  You know how small they are?  Kinda easy to click on the wrong one?

Me neither.