Hunting switched earth relay for motorcycle

Thread Starter

Jackson95

Joined Jan 14, 2018
4
Hey all, new to the forum and hoping for some help.

I build custom motorcycles and the latest project is heavily based on a smart ecu unit controlled by a Bluetooth device.

Apart from that, the bike has obvious warning signs (indicators,neutral,oil level)


The issue is, the bike uses a oil level switch. When the oil level is correct it supplies a earth to the warning light through a controller.

Problem with that is that obviously this leaves the light on constantly when riding.

Does anybody know of a small relay that when receiving a earth would not give out a earth supply and will give a earth when not receiving a signal from the switch?

Will need to be pretty small as there’s not a lot of room.
I’m aware conventional automotive relays take a signal and supply an output but no good for me.

If this is possible, I’m in London and need one ASAP so if anyone knows is I can get something like this in Maplins etc?

Thanks in advance
J
 

GopherT

Joined Nov 23, 2012
8,012
Hey all, new to the forum and hoping for some help.

I build custom motorcycles and the latest project is heavily based on a smart ecu unit controlled by a Bluetooth device.

Apart from that, the bike has obvious warning signs (indicators,neutral,oil level)


The issue is, the bike uses a oil level switch. When the oil level is correct it supplies a earth to the warning light through a controller.

Problem with that is that obviously this leaves the light on constantly when riding.

Does anybody know of a small relay that when receiving a earth would not give out a earth supply and will give a earth when not receiving a signal from the switch?

Will need to be pretty small as there’s not a lot of room.
I’m aware conventional automotive relays take a signal and supply an output but no good for me.

If this is possible, I’m in London and need one ASAP so if anyone knows is I can get something like this in Maplins etc?

Thanks in advance
J
8699BDBF-070D-4472-921B-B9F8D6B50613.jpeg
 

Thread Starter

Jackson95

Joined Jan 14, 2018
4
In the diagram, if I gave a constant 12v to the coil (ignition controlled)
Then the earth from the coil runs through the switch to earth.

Then my pickup which needs a earth would be what you have labelled ‘out’?

Then a constant 12v and earth on the right side.

If that all made sense?
 

Thread Starter

Jackson95

Joined Jan 14, 2018
4
Hope my drawing makes sense

Basically is point 1 and 2 have 12v
When point 3 has earth then point 5 will get 12v

When point 3 doesn’t have a earth then point 5 will be earth?

Think that’s correct,
Just out of interest, what is the need for the 1k resistor?

Thanks
 

Attachments

GopherT

Joined Nov 23, 2012
8,012
Hope my drawing makes sense

Basically is point 1 and 2 have 12v
When point 3 has earth then point 5 will get 12v

When point 3 doesn’t have a earth then point 5 will be earth?

Think that’s correct,
Just out of interest, what is the need for the 1k resistor?

Thanks
Yes, point 5 will be at ground when point 3 "loses ground".

I would just use different phrases. I would say, point 5 would be "pulled low" if the coil is not energized (circuit to the coil is not complete).

Without the 1k resistor, there would be a short circuit from +12v to ground through the relay. One second for an alternative.
 

Thread Starter

Jackson95

Joined Jan 14, 2018
4
Ok great, so with your layout I won’t need the resistor because no 12v will be going directly to ground.

I’ll have to swap the top right earth and 12c so the switch works the other way round. But I don’t actually need that 12v so il run nothing.

all seems good, I’ll give it a go tomorrow
Thanks guys
 
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