Questions re: GHurd Controllers

[paulrogers6]

Dear All

I have one of GHurd's controllers controlling a dump load.  I'd now like to add another controller as an LVD.  The current controller is about 5m away from the batteries and using some old 2.5mm multistrand copper cable to "sense" the battery voltage. My first question is could both controllers use the same pair of (sensor) wires to the batteries or would they some how interfere with one other?

Also, having read some of the posts here,  I now think I ought to have some form of fuse on the sensor wire to the battery.  What sought of amperage should the fuse be?  Presumably the controllers do not draw much current?

Thanks

Paul

[ghurd]

Wow.  2.5mm wire is about #10.5?

I usually use about 0.7mm (#21~22).

I believe 2 controllers sharing the same sensor wire with wire that large will not cause any problems.

Depending on how it is assembled, it will pull a max of about 10 or 12ma.

Adding a fuse may cause more trouble than sharing the wires under these conditions.

Maybe a 0.5 or 1A fast blow would be suitable.

Very low amp fuses (100ma) could (possibly?) add enough resistance to tighten the hysteresis considerably.

G-

[paulrogers6]

Hi Glen

Thanks for the reply.

Do you not normally bother with a fuse?  Is it more trouble than it's worth?

Is the 0.5 or 1A fuse gonna cause similiar problems?

I thought that the bigger the better for the cable so it had as little impact as possible on the voltage the controller sees.  That's right isn't it? or have I got it all muddled up again.

Cheers

Paul

[ghurd]

I do not normally use a fuse on the controller circuit itself, though I probably should.

It would take some very catastrophic failures to get 25ma through the circuit.  Even a short on the output wire (to fet gates) will only pull about 110ma, and should not damage the circuit (usually).

I believe the biggest danger is the wires being shorted from damage, or operator error.

A fuse should be very near the battery.

A half or 1A fuse should not cause problems. Not sure a 250ma would cause problems.

It should be fast blow.

Bigger is better for cable.  

"so it had as little impact as possible on the voltage the controller sees"

Correct. But after a certain point the difference is minute.

And that wire passed that point!

If you used #22 like I use, I would say you should run a 2nd cable.

If you used #22 like I use, it would be far more susceptible to damage.

The large wire will not cause any problems.

A cheapie fuse holder may cause problems.

Get one with solid clips on each end.  Not one of those white plastic tubes that come with cheap car stereos.

A poor connection between the fuse and fuse holder could wreak havoc on the controller's voltage being sensed, and that kind of issue is Very difficult to find.

Might consider gold plated holders and fuses, if they are made in that size.

G-

[paulrogers6]

Glen

Again thanks for the advice.  That's what I was worried about was physical damage to the cable that might cause a short/fire.

I'll look out for a decent fuse.

Again many thanks.

Paul