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selection of relay for driving an immersion rod

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issac newton

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i am designing a heating element control system. i am looking for a relay(with 5V input voltage if possible or 12V) which can control an immersion rod with specification 16-A & 250 V AC. The following are my questions.

1. the heater has to be driven with power sockets(type M sockets -16A). can i use normal sockets of "type D"(which produces max current of 15A). what will happen if i use this. will the heating process be slow because of lower current driving capacity of the socket or the effect will create some problems ?

2. to control this heating element i am using MSP 430G2231. is there any switching device instead of relays like mosfets which work out cheaper for controlling the heater with specified ratings.

3. which relay might suit my requirements. cheap and best ones.

4. i am using LM35 as my temperature sensor. please suggest me with some other best,cheap and user friendly sensors with resolution upto 0.5 degree.

thank you all.
 

sky_123

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Are you sure the heating element consumes 16A? Also, 250V seems unlikely, given that mains is 230V or 110V.
 

issac newton

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the rating on the heating rod says this spec(may be it is the maximum spec). my rod does work with 230 V. but it uses a power socket as mentioned above(type M) so shud consume 16A. correct me if i am wrong.
 

sky_123

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No, this is incorrect. You need to check the specs of the immersion rod. If you don't know, then yes you can use a 16A capable relay.
Are you familiar with techniques to safely switch mains with relays? If not, be careful; some tips are:
Keep the low power side well separated, use protection devices like fuses, make sure you can't touch any high voltage points, etc.
Don't use the small PCB relays unless you really use a PCB (some people have been known to use a stripboard, which is highly
dangerous). You could use the plug-in relays that fit into bases that have screw terminals.

A semiconductor method will require some engineering, you could investigate triacs as one option.
You could use a ready-built SSR, but a 16A one may be expensive and may require heatsinking.
Regarding temp sensors, SE95 has extremely good resolution as you require, but that doesn't mean accuracy is extremely good too.
I don't know of any accurate to 0.5degC.
 

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