Need to source an 'arse about face' Brake light switch

[Wreford Miles]

My HP2 has a non standard front brake with a hydraulic switch which operates in a way that I expect many do - When the brake is applied the switch closes the circuit and the brake light works.

The original BMW (HP2 Mega Moto) switch it appears worked the other way around - it opens when the brake was applied

Q: Does anyone know where I could get a hydraulic switch which works in this way?

Cheers

Wreford

 

[RobertG]

If you can't get a switch you could add a relay with a set of normally closed contact.

 

[Wreford Miles]

If you can't get a switch you could add a relay with a set of normally closed contact.

I was trying to think that one through but my head was hurting

So the current swith would close which would cause a relay to open, so if the brake light connections where connected to the relay they would think the brake was on...

Would the relay not need a power feed?

 

[Wreford Miles]

I'm drawing a blank on finding a switch that breaks the connection ratner than makes it when the brake is applied so I may have to look at the relay route

Any views on how to do this or other options?

Cheers

Wreford

 

[Fanum]

My HP2 has a non standard front brake with a hydraulic switch which operates in a way that I expect many do - When the brake is applied the switch closes the circuit and the brake light works.

The original BMW (HP2 Mega Moto) switch it appears worked the other way around - it opens when the brake was applied

Q: Does anyone know where I could get a hydraulic switch which works in this way?

Cheers

Wreford

Is it not just a matter of wiring a conventional switch 'backwards' so the open position creates the circuit rather than breaking it?

 

[Wreford Miles]

Is it not just a matter of wiring a conventional switch 'backwards' so the open position creates the circuit rather than breaking it?

I dont think so as the switch only has one action to close a normally open connection or open a normally closed connection.

Hydraulic ones seem to close a 'normally open' switch

 

[RobertG]

I was trying to think that one through but my head was hurting

So the current swith would close which would cause a relay to open, so if the brake light connections where connected to the relay they would think the brake was on...

Would the relay not need a power feed?

Something like this (assuming the switch closes the positive - check with meter, if not just reverse polarity of the diagram)

 

[RobertG]

Is it not just a matter of wiring a conventional switch 'backwards' so the open position creates the circuit rather than breaking it?

Would need to be a two way switch with both a normally open and a normally closed connection. Unlikely to be fitted, but definitely worth checking.

 

[ianboydsnr]

I was trying to think that one through but my head was hurting

So the current swith would close which would cause a relay to open, so if the brake light connections where connected to the relay they would think the brake was on...

Would the relay not need a power feed?

You need a 5 pin relay,

You use the hydraulic switch you have to operate the relay, so power to the hydraulic switch, power from the switch to the relay, you then wire the original switch circuit to the relay using the extra pin 87A rather than the 87 pin the energised relay then turns off the power to the original circuit.

 

[Wreford Miles]

You need a 5 pin relay,

You use the hydraulic switch you have to operate the relay, so power to the hydraulic switch, power from the switch to the relay, you then wire the original switch circuit to the relay using the extra pin 87A rather than the 87 pin the energised relay then turns off the power to the original circuit.

That make sense so the power is all on the brake lever side of the relay and the relay just closes an open connection on the command of the brake switch closing a normally open connection.

A lot of friggin wire to solve a problem but unless I can fined a normally closed hydraulic switch I'm a bit stuck

 

[rudiemoto]

Had to use a 5 pin relay
All good now

 

[Cook1e]

Sorry too late

But if anybody else has the same problem...

http://www.pvl.co.uk/pressure_switches.html

 

[Wreford Miles]

But if anybody else has the same problem...

http://www.pvl.co.uk/pressure_switches.html

Not to late... I'm still looking for a solution

 

[Cook1e]

Ah yes - saw Rudie had gone with the relay, thought that was it, but you were OP.

Well, search "hydraulic pressure switch" rather than specifically "brake switch" and normally closed (N/C) is what you need.

Good luck!

Ian

 

[Wreford Miles]

Ah yes - saw Rudie had gone with the relay, thought that was it, but you were OP.

Well, search "hydraulic pressure switch" rather than specifically "brake switch" and normally closed (N/C) is what you need.

Good luck!

Ian

Ian you are a star

Just ordered one of these: http://www.pvl.co.uk/user/datafaxes/Elettrotec/PMN_pressure_switch.pdf

 

[Cook1e]

Ian you are a star

Nah, used to work with tame engineers is all

Glad to be of help.

 

[Wreford Miles]

Just ordered one of these: http://www.pvl.co.uk/user/datafaxes/Elettrotec/PMN_pressure_switch.pdf

Need a plan B as the thread is not long enough or designed to work in a banjo.

Plan B might include:
Finding a banjo with two connections and have one with a short feed going to this switch

 

[Wreford Miles]

I'm now thinking relay is the best option

5 pin relay
Connect brake light lead that is NC to 30 and 87a
Wire one side of the in place hydraulic switch which is NO to a power feed (not sure which power feed is best)
Then and connect to 85
Then connect 86 to the bike for an earth

In theory I apply the front brake which closes the NO hydraulic switch, which then triggers the internal solenoid to make a connection between 30 and 87 and in the process breaking the connection between 30 and 87a meaning the brake light comes on

If I'm right my challenge is where do I take the power from and how should I earth it.

 

[Cook1e]

Need a plan B as the thread is not long enough or designed to work in a banjo.

Plan B might include:
Finding a banjo with two connections and have one with a short feed going to this switch

Sorry, I wasn't aware of the required thread. Anything here to help? http://www.earls.co.uk/earls/adapters/brakesystemadapters.html

Or these are cheap & common:
http://www.wemoto.com/parts/picture/hl-171020_5/

Replace the bleed nipple with your switch.

Mucking about with relays seems over-complex (more wires, connections & switches to go wrong).

Failing all that, find a friendly machinist to make an adaptor.

 

[Wreford Miles]

Sorry, I wasn't aware of the required thread. Anything here to help? http://www.earls.co.uk/earls/adapters/brakesystemadapters.html

Or these are cheap & common:
http://www.wemoto.com/parts/picture/hl-171020_5/

Replace the bleed nipple with your switch.

Mucking about with relays seems over-complex (more wires, connections & switches to go wrong).

Failing all that, find a friendly machinist to make an adaptor.

Thanks Ian,

I did call Earls for a switch ( they only had NO) but the adaptor route looks very promising