I have this relay circuit but it doesnt work the way i want it to. I have a Panasonic relay switch.

http://datasheet.octopart.com/DK1A-12V-F-Panasonic-datasheet-148175.pdf

It is a SPST/NO relay. I need to turn a cartridge heater ON/OFF with the relay. My circuit gives out 8V to switch the relay and it works fine. I check the connectivity of the relay, switchin it on and off and the connectivity breaks and connects accordingly. But when I take the AC supply and connect it with the heater, the whole circuit works as a NC circuit. So the cartridge heater works when there is no 8V going to the relay and stops working when the 8V is supplied. I have attached a very simple outline of the circuit I have.

 

I admit it - I'm stumped. Can you hear the contacts close when you apply AC? We are talking about the "single side stable" part, right, the one with just 4 pins?

 

Can you provide us with the exact part number of the relay that you are using so that we can confirm its operation with the specification that you have link to in your post?

hgmjr

 

How is the circuit being built? Is it a pcb, breadboard, or just wires on bare component?

 

Tha part number of the relay is DK1A 12V-F. The control signal for the relay comes from a breadboard but the relay circuit is just a couple of 18 gauge stranded wires. The thing I cannot understand is that now even if the relay is lifted from the bread board and the ac wires connected through the relay, power source and heater, the heater kicks in.

 

I admit it - I'm stumped. Can you hear the contacts close when you apply AC? We are talking about the "single side stable" part, right, the one with just 4 pins?

I did not try that. I am using the relay with a total of four pins. Two are the dc side and the other two are the AC side. Let me try and figure out when are the contacts closing when I apply the AC.

 

That's a N/O SPST - 12VDC relay. A 12V relay may hold closed down to 8V but it can't be reliably energized at 8V, if at all.

http://octopart.com/dk1a-12v-f-panasonic-102170#technical_specs

http://search.digikey.com/scripts/d...t_dkc_buynow&site=us&lang=en&name=255-2059-ND

Here's the Data Sheet:
http://pewa.panasonic.com/assets/pcsd/catalog/dk-catalog.pdf

 

That's a N/O SPST - 12VDC relay. A 12V relay may hold closed down to 8V but it can't be reliably energized at 8V, if at all.

I understand that part, which is why i tried testing without any load. But atleast if it doesnt energize the circuit should be an open circuit. That is what I dont understand. Even without being energized the circuit is closed.

 

If you have no power to the coil and yet the contacts are closed, then it's toast!

 

But it works without the AC side connected. So it shouldn't be dead right?

 

But it works without the AC side connected. So it shouldn't be dead right?

Are the contacts stuck closed?

 

I tried the the circuit with another relay of 24V and it works fine. So I guess CDRIVE was right...

 

Most likely the contacts were probably subjected to an extreme over current condition, like a shorted component that it supplied current to. This, in turn fused the contacts together. Not that uncommon.