How do I calculated a Fuse and Switch for a DC Circuit using a Car Battery ( isolated ) safely.

Thread Starter

RandyFL

Joined Aug 28, 2014
148
Looks ok, you can use an automotive relay to power the motor, like one of these..

http://m.ebay.com/itm/2-LOT-TEMCo-1...ss-Socket-Automotive-/381339530351?nav=SEARCH
Dave,
The TEMco relay came in yesterday... according to your circuit diagram:
here is the circuit with a switch, relay, overload fuse...
View attachment 101537
the wires didn't come numbered...they came three large wires ( yellow, red and blue ) and two smaller ones ( black and white )...
also the relay comes into two parts ( part a. the assembly with wires ( CN0174 )and part b. the top part ( CN0171 ) )...
here comes the really newbie question :) which colored wire goes where...

also... 1. the large wires ( yellow, red and blue wires ) aren't 8 gauge wires ( I bought 8 gauge AWG because... looking at the picture of this relay I knew the wires weren't as big as 8 gauge AWG ) 2. since the relay isn't 8 gauge AWG it is the weakest link into this circuit ( IMHO ( In My Humble Opinion )) 3. Since my battery is a lawn mower battery DC 12 volt 300 CCA and this is just a proto type model the circuit and the motor won't used continually or a heavy demand I decided to go with 8 gauge ... In a real situation ... the correct wire size should be rated at the battery size ( or the demand size ) ... meaning ... My sailboat had a main switch that connected to 4 marine heavy duty size batteries ... the house part of the main switch had 3 marine batteries that would make this circuit toast ( or worst ) if something went wrong ... the 4th battery of the main switch went to the engine ( 37 hp diesel ... the sailboat was 37 foot O'Day and I had electricians do the electrical work )
Lastly... I bought a ammeter from Ebay that is DC 200 volt 300 amp ... where in the circuit should I place it...

Thanx in advance
R
 

Thread Starter

RandyFL

Joined Aug 28, 2014
148
Hello,
Could you help me with the relay...
The TEMco relay came in last week...
according to the circuit diagram that Dave provided ( above ^ ) He gave out numbers but not the colors...
they came three large wires ( yellow, red and blue ) and two smaller ones ( black and white )...
also the relay comes into two parts ( part a. the assembly with wires ( CN0174 )and part b. the top part ( CN0171 ) )...
:) which colored wire goes where...
I'm assuming the red goes to positive and the black goes to ground.

Thanx in advance
R
 

Dodgydave

Joined Jun 22, 2012
11,285
Can you show a picture of it, or if you have a multimeter, measure the coil resistance that will give you two wires,(black and white)

the other 3 will be the contacts, one will be the common, probably Red.
 
Last edited:

Thread Starter

RandyFL

Joined Aug 28, 2014
148
Can you show a picture of it, or if you have a multimeter, measure the coil resistance that will give you two wires,(black and white)

the other 3 will be the contacts, one will be the common, probably Red.
Dave,
Hope its large enough to see...:)
I bought 2 of them in case I screw up...
 

Thread Starter

RandyFL

Joined Aug 28, 2014
148
Click on "dimensions and wiring diagram" bottom right, it shows you the colours and numbers.

Yellow common,30
Red Nc,87a
Blue No.87
Black- White coil.85,86
Thanx Dave,
Hopefully I'll get my bus bars this week and finish building this...
When the circuit is up and running I'll post it... and come back and ask a few questions and wrap this part up

thanx again for the help
R
 

Thread Starter

RandyFL

Joined Aug 28, 2014
148
Thanx Dave,
Hopefully I'll get my bus bars this week and finish building this...
When the circuit is up and running I'll post it... and come back and ask a few questions and wrap this part up

thanx again for the help
R
1 May 16 Update:
Finished the circuit. It is up and running ( took awhile to get all the parts and then to actually build the circuit - and then to test it and then why it wasn't running - but that's all done ) A few questions ...
1. Why a relay? couldn't it have been setup without it...what are the pros and cons...
2. I haven't done any tests on the motor or the circuit per se ( it started and I then shut everything down ) or how much volts or amps is actually being used. Whenst I get the 2nd part hooked up should I be looking for heat problems or ... what comes to mind about safety? Or is the two backup safety things ( I put a fuse holder and a circuit breaker in place )
 

Thread Starter

RandyFL

Joined Aug 28, 2014
148
1 May 16 Update:
Finished the circuit. It is up and running ( took awhile to get all the parts and then to actually build the circuit - and then to test it and then why it wasn't running - but that's all done ) A few questions ...
1. Why a relay? couldn't it have been setup without it...what are the pros and cons...
2. I haven't done any tests on the motor or the circuit per se ( it started and I then shut everything down ) or how much volts or amps is actually being used. Whenst I get the 2nd part hooked up should I be looking for heat problems or ... what comes to mind about safety? Or is the two backup safety things ( I put a fuse holder and a circuit breaker in place )
I forgot the picture...IMG_2537motor.JPG
 

Thread Starter

RandyFL

Joined Aug 28, 2014
148
Click on "dimensions and wiring diagram" bottom right, it shows you the colours and numbers.

Yellow common,30
Red Nc,87a
Blue No.87
Black- White coil.85,86
1 May 16 Update:
Finished the circuit. It is up and running ( took awhile to get all the parts and then to actually build the circuit - and then to test it and then why it wasn't running - but that's all done ) A few questions ...
1. Why a relay? couldn't it have been setup without it...what are the pros and cons...
2. I haven't done any tests on the motor or the circuit per se ( it started and I then shut everything down ) or how much volts or amps is actually being used. Whenst I get the 2nd part hooked up should I be looking for heat problems or ... what comes to mind about safety? Or is the two backup safety things ( I put a fuse holder and a circuit breaker in place )

anything else I should be concerned about with this circuit...

thanx in advance
 
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