Easy temperature switch

Gannon · Post by **Gannon** » Tue Nov 26, 2013 8:14 pm

Dad asked me to come up with a over temperature watchdog for a stationary diesel engine (irrigation pump) that would turn it off in the event of over temperature.

I was looking at these first for $150

Then these for $13

Then I saw one of these for $1.46

and it got me thinking... why does it need a display if its for a stationary un-manned engine?

So a little searching landed me with these for roughly the same price and they are available in both normally open and normally closed

I can crimp one in a 25mm2 cable crimp or fold aluminium or copper around it and bolt it to the head of the engine and then wire it to a horn relay in series with the ignition switch so the engine operates normally until the chosen temperature (you can choose almost any temperature between 40 and 200deg c in 5 deg steps) but once the temperature is reached, it opens, drops the relay out and kills the engine.

But a normally open one could easily control a radiator fan or an red light/alarm on the dash. Its cheap and should be foolproof and reliable.

Wooster · Post by **Wooster** » Wed Nov 27, 2013 7:39 am

Initiative, truely the Aussie way, well done mate

If only we could do the same with number 8 fencing wire?

cheers
Ray

vincentvega · Post by **vincentvega** » Wed Nov 27, 2013 10:57 am

Don't crimp it into the cable lug. Just sit it in there and fill it with epoxy.

The one in your first image is made this way. I asked the manufacturer a few years ago.

Gannon · Post by **Gannon** » Wed Nov 27, 2013 3:38 pm

I didnt mean I was gonna use the crimping pliers on it and crush it. Merely push it in and compress it just enough to hold it in place and then heatshrink it.

vincentvega · Post by **vincentvega** » Wed Nov 27, 2013 5:53 pm

Epoxy is the way to go. air gaps aren't the best way to get heat transfer.

The TM2 sensor is done as you described, then filled with epoxy.

Gannon · Post by **Gannon** » Wed Nov 27, 2013 6:19 pm

No worries.

Silverbullet · Post by **Silverbullet** » Wed Nov 27, 2013 6:34 pm

And epoxy isn't an insulator? Not doubting just asking

Thanks for the info Gannon very useful.

Gannon · Post by **Gannon** » Thu Nov 28, 2013 8:26 am

Silverbullet, I assume you are referring to thermal insulator not electrical? I'd say epoxy is a better heat conductor than air gaps. If you really wanted to be thorough you could use heatsink glue.

I was expecting steptoe to take interest in this thread. Where are you jono?

Sent from my new touchy phone thingy

Silverbullet · Post by **Silverbullet** » Thu Nov 28, 2013 5:10 pm

Gannon wrote:Silverbullet, I assume you are referring to thermal insulator not electrical? I'd say epoxy is a better heat conductor than air gaps. If you really wanted to be thorough you could use heatsink glue.

I was expecting steptoe to take interest in this thread. Where are you jono?

Sent from my new touchy phone thingy

Yeah I meant thermal, only cause my train of thought leads me to comparing epoxy resin to plastic. Yes better than an air gap anyway.

Yeah where is Jonno, usually jumps on this stuff

steptoe · Post by **steptoe** » Thu Nov 28, 2013 5:15 pm

power down when I went to reply ??
Those self imported from HK , the sensor is a nice tight fit into a 4mm hole, no epoxy needed in my applications and they are working well. I have figured it is probably better utilised to switch fans on and off rather than an over temp alert as is how I have rigged them.

Another good find by Gannon

Phizinza · Post by **Phizinza** » Tue Apr 08, 2014 10:32 am

Crimp it, then fill the air gaps with thermal paste or even grease.