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
In it's simplest form, a diode that can handle the peak motor current and reverse voltage of the power supply.
Dennis,
How was your 2015?

Thanx.. all who contributed to this thread. I will order the parts and build asap...
Theres a part that's sitting here ( but I will deal with it later ) motor control that I bought from Canakit... but as I say I'll put that in later...

R
 

Dodgydave

Joined Jun 22, 2012
11,285
Thats a 12V pwm motor speed control, just put the controller in place of the motor, and connect the motor to the controller,

I use paint to draw the circuits.
 

Thread Starter

RandyFL

Joined Aug 28, 2014
148
here is the circuit with a switch, relay, overload fuse...


View attachment 101537
Dave,
I forgot about the cables ( wire )... what size wire should I use for this project...?
just above the rating of the fuse 80 amp or just above the rating of the battery ( 12 volts 300 CCA )
i'm sure a screwdriver or wrench starts to glow when improperly placed :)

R
 

Thread Starter

RandyFL

Joined Aug 28, 2014
148
Go for just above fuse rating or higher if its within your budget.
Dave,
I was thinking about this all day yesterday...and checking the posts here this morning...
1. I don't know if I found
this...
http://www.ebay.com/itm/In-Line-Car...802189?hash=item419af7c08d:g:PBYAAOSwyQtVzOlU

here on the posts ( or if I found it on my own ) my question is this...
why would I build a circuit in 6 gauge wire when the fuse assembly is built in 8 gauge wire... ( my thinking is whilest the motor is running at x speed ... the least gauge wire is going to get the hottest ... my reasoning would build a 6 or 4 gauge wire with a fuse of say 60 ( or whatever ) amp rating so the wire stays cool...and if a surge came ( I don't know if surges come in DC ) it would take out the 60 amp fuse .........

thanx
R
 

Dodgydave

Joined Jun 22, 2012
11,285
Use the biggest size wire that suits your current limit., so if you're using a 50 amp fuse, you need 60 amp wire or higher.
 

Thread Starter

RandyFL

Joined Aug 28, 2014
148
Use the biggest size wire that suits your current limit., so if you're using a 50 amp fuse, you need 60 amp wire or higher.
Is there such a thing as a diode holder... or do I hand solder it onto the wire.

Diode I will go with...:
MUR860 MOTOROLA DIODE ULTRA FAST 600V 8A TO 220AC

here:
http://www.ebay.com/itm/121214036013

calculations ( if correct )
600 volts
8 amps
75 ohms
4800 watts

versus ( if this a correct way to judge ... which is probably not ) :)
12 volts
80 amps
.12 ohms
1200 watts

all the best
R
 

Thread Starter

RandyFL

Joined Aug 28, 2014
148
The diode is soldered on the motor wires,
I bought a wire stripper when I got involved in electronics ( in 2014 - I'm a late bloomer ) anyway the instrument I bought does a nice job with small wire... my question is what do ppl use for larger wire

any suggestions are most welcome
cutter \ stripper \ crimpers \ connectors \ heat-shrink tubes ...

R
 

Thread Starter

RandyFL

Joined Aug 28, 2014
148
I use a craft knife,wire cutters or soldering iron to take a chunk of insulation off.
update...
I had to wait until my funds were up to speed...ordered all the parts I needed do this project and then some...

Question
I hadn't included bus bar (s) into the order ( i'll wait for the next order )
Since I will be making different connections for different things ( clips ( or clamps ) to quick connect to battery as versus permanent connections ) ... how does this change the diagram or schematic....................
Should I use black and red bus bar ( s ) or strictly black, and mark them.

All the Best
R
 

Thread Starter

RandyFL

Joined Aug 28, 2014
148

Thread Starter

RandyFL

Joined Aug 28, 2014
148
Get the Amazon red one.
A. I would like to build a Ammeter ( with various shunts ) that I could leave in a circuit, like the one I am building. The circuit, that I am building isn't going to be permanent until I work out all the variables ( like what I intend to use the circuit for ).
B. Is there a way to combine a Apple pencil with an iPad and use the App Paint to draw circuits with? I wanted to see your perspective about these ideas...
 
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