Reversing voltage.

Other Hardware General Electronics
1

Morning All!

First post so here goes...

I have an issue with a 24v system on a doosan excavator. I want to install a device that requires a switched 24v feed, permanent 24v feed and an earth.

However, it seems the system has reversed voltage, as in feeds are live when the machine isn't in use and dead when the ignition is turned.

My question is, is there a device or component i can connect in line to return this voltage to what I require? (For example, when I switch the ignition I get 24v instead of nothing?) without affecting the overall electrical system of the excavator?

Any help with this would be great!

Thanks.

2

I suspect your understanding of the circuit is probably flawed. It's quite possible that the SWITCH is on the GND side of the "device".

I think you need to give a bit more information and ideally a schematic of what you have. You'll also need some idea of the current demands required.

3

When reversed you still get access to a 24v line? Just they swapped?

4

Provide the circuit.

If you do not have the circuit - even a diagram you have traced out for yourself - you have little or no hope of solving the problem.

5

It's the paradox of the riddle inside an enigma wrapped up in a mystery

6

Hi, the system of placing the isolating switch in the gnd lead of the battery is somewhat common practice in heavy moving equipment.

Tom......... :slight_smile:

7

Thanks for the replys everyone,

I'm afraid I don't have a schematic of this system, I'm just testing feeds.

The best I can describe it as is what I've just done...

At the IGN barrel all feeds are live. They then drop in voltage when the excavator is IGN on.

All the wiring I can see goes to a large ECU and out of the other side of the ECU up to the main fuse box in the cab.

Voltage signals at the fuse box are similar to the ones at the IGN barrel.. Once the IGN is on feeds go dead

I've since been to another excavator that has a similar device installed already and has its voltage signals taken from the fuse box...

However, to get the voltage signal required there is what seems to be a sensor placed/clipped over the wire from the fusebox soldered onto the wire from the device.

Testing this shows the signal I require.
Any ideas people? Is there some way I could post a photo here?

Cheers.

8

Sorry! Just found the attachments icon.

Photo is of a component/sensor of some sort that's altering the voltage signal on the chosen wires to IGN 24v when IGN is turned to on, instead of it going dead.

Anyone seen these before?

Thanks

9

Still none the wiser. I see no image or link in your post.

10

Photos are to big to post here sorry.

11

MartinScu:
Photos are to big to post here sorry.

So open in Paint, shrink, save-as, post.

12

here is a photo

voltage.jpg
voltage.jpg490×653 95.6 KB

13

That looks like an insulation displacement connector. It's just a method of connecting a wire to an existing one without having to strip the cable.

14

Thanks KenF!

I'd never seen one before, so in you're opinion, this would have nothing to do with the different voltage signal readings?

Cheers.

15

It's just a connector. Wouldn't have a clue what it's connecting to what.