Electrical Engineers - need small cheap relay

[dullard]

Currently I have this type of input/output module. It takes a ~4 VDC, ~18 mA signal and relays a 24 VDC, 0.42 A line.

I want to play with ~20 of them. Is there any way of doing this smaller and cheaper? All I need is to turn on/off 24V equipment with the 4 V signal.

 

[jmcoreymv]

What type of isolation do you need, if any?

 

[promposive]

http://www.rason.org/Projects/transwit/transwit.htm
Use a transistor to operate an individual relay of your choice use a relay with a 24v coil, and a 24v (or higher) load ability. This way you only need the 2 power sources, or use a lower powered relay coil with another power source.
Or if your load is lower amperage, just use the transistor.

 

[FoBoT]

dang , those are expensive
shirley you can find something cheaper

 

[promposive]

http://bgmicro.com/prodinfo.asp?prodid=TRNTIP120
using something like this schematic: link
60V 5AMP Transistor

Combine with heatsinks if just using this, these guys get hot.

or use it with an aditional relay,
http://www.bgmicro.com/prodinfo.asp?prodid=REL1021
http://www.bgmicro.com/prodinfo.asp?prodid=REL1059
http://www.bgmicro.com/prodinfo.asp?prodid=REL1078

 

[dullard]

Originally posted by: FoBoT
dang , those are expensive
shirley you can find something cheaper

Yes, those are expensive. And please don't call me Shirley. (Airplane I/II movie reference).

Originally posted by: jmcoreymv
What type of isolation do you need, if any?

~4 VDC signal comes straight from the computer, so I need enough isolation that the 24 VDC signal can't harm a computer. It is supposed to be 5 VDC but computer power supplies never seem to give that much.

Originally posted by: C0BRA99
...

Thanks, Cobra99, I'll take a look at those after the weekend.