View Full Version : Need help on connecting a blast relay

06-01-2006, 11:53 AM
I have build a Difalco controller kit from DD231-15 and DD242.
I now want to connect a Blast relay with an on/off switch. I know I can turn off the relay by cuting (using the switch) the control wire.
Does the white wire need to be cut off from the power connector?

If so, can someone help me out with a simple chematic on how connect the white wire?

06-01-2006, 11:27 PM

I used the Difalco blast relay on my own controllers before finding my own source of 40A relays and surge protectors. You should be able to wire it the same as I do on the Linear 100.

The relay coil is energized by current flowing from the control wire though the RED wire to track ground. The WHITE and BLACK wires go across the relay contacts and have nothing to do with energizing the relay coil.

Hold the relay so the terminals face you as shown below and wire as indicated:

-------------- xxx
---------xxx-----------| BLACK


Bend the BLACK terminal flat.

Be sure to install the surge protector between the RED and CONTROL terminals. It will absorb the inductive kick of the coil when it's de-energized. The surge protector is bidirectional so you don't have to worry about polarity as with a diode.


06-02-2006, 04:35 AM

Thanx for the info, but what do I use as a surge protector?

06-02-2006, 09:09 AM

The surge protector is included in the Difalco blast relay kit. No need to order anything else.


06-02-2006, 11:21 AM
Sorry, nothing unfamiliar in the relay package. Just the relay, 2 length of wire, some cable tie and a screw.
The istructions did not say anything about any surge protector.

06-02-2006, 03:31 PM
Interesting. Mine always came with the surge protectors and I made my last buy about 2 months ago.

The part number is SA20CA and it's made by several electronics companies. It's commonly known as a bidirectional TVS diode in the eletronics biz.

There are several small order catalog distributors that carry this device and will sell it in single unit quantities.

I tried checking stock with the European distributor Farnell InOne but their website is down until Sunday morning for maintainance. (I'm a semiconductor marketing manager with their sister company in the US.) Here's the link:

Farnell InOne (http://www.farnell.com)

I've (Newark InOne that is) have no stock but I just checked and both Mouser and Digikey have them. Like Newark, Mouser has no minimum handling fee for orders under $25. I believe they both ship internationally. Here are links to their websites:

Mouser (http://www.mouser.com)
Digikey (http://www.digikey.com)


06-02-2006, 03:52 PM

Again, thanks for the info.
I will order from Farnell InOne in Norway