Low voltage relays

[tigersaw]

Good idea.
I'll trawl through the RS catalogue tomorrow if I have time, see what they have. Since the LED used very small current I dont think it will drive a relay directly, might be better to find a little circuit with a relay driver built in, and maybe then it can be simply modified to self cancel after a second or two

[tigersaw]

Originally Posted by Baph

Why not mount a light under the screen (top of the "dash") - a red LED is eye catching enough even on a summer's bright day.

I know first hand.

Thats included, though I agree with the OP - its not enough

[DarrenSV650S]

I want a horn! *spits dummy*

I don't want to be constantly looking down to see if the light is on. I'd rather just not have to look. I've mounted the inforad's light in the hole in the stem because it was the neatest option I could think of. But because it is there I don't see it easily.

So is that first relay suitable baph?

[DarrenSV650S]

Originally Posted by tigersaw

Good idea.
I'll trawl through the RS catalogue tomorrow if I have time, see what they have. Since the LED used very small current I dont think it will drive a relay directly, might be better to find a little circuit with a relay driver built in, and maybe then it can be simply modified to self cancel after a second or two

Oooh a self cancel would be great. I set the inforad to it's lowest setting but that still means it comes on 15 seconds before the camera, plus a little while after I've passed the camera

TBH, for your application, I wouldn't bother using a relay.

I'd do the following:

Buy a 12v transistor, and connect the emitter leg to ground. Your 3v pulse to the base leg, a 270 Ohm resistor to the collector leg, and the 12v supply horn wire to the resistor.

Don't put this between the horn & horn switch, but on the other side of the horn. Should work a treat as the SV horn is fed a constant 12v, and is only grounded when you hit the button. This is basically adding another switch capable of grounding the horn.

EDIT: Non of the above will achieve self cancelling... if you want that you're looking at using a timer as well probably.

[tigersaw]

just looked at some kits - about £6 for a kit that has a trigger input and adjustable timer output, and about £6 for a police siren, fire brigade, emergency vehicle and machine gun sound generator.
Thinking required to interface the timer kit to the inforad (which has a relay output for your horn), studied the cct of the siren, I reckon it would be pretty loud enough

[DarrenSV650S]

Baph I won't be using the original horn wiring. I've got that on a relay which is running a stebel horn. But the original horn is still on the bike so I can get a feed from the stebel relay to the original horn

Where did you see that kit tiger?

[tigersaw]

http://www.maplin.co.uk/Module.aspx?ModuleNo=25224 or
http://www.maplin.co.uk/Module.aspx?ModuleNo=3315

Both will need modifying

modify the trigger circuit and set output to say 5 secs.
be nice to make it so that when the red lamp is flashing it will constantly retrigger and cause a constant 'horn' - until red led is constant then it will time out.

I'm off to bed now, but I'll think about it further and try and knock something up in the coming week or two

[DarrenSV650S]

Originally Posted by tigersaw

Thinking required to interface the timer kit to the inforad (which has a relay output for your horn)

Wouldn't I just connect the inforad's wires to the control side of the relay and then the other side would switch the horns feed?

[tigersaw]

Originally Posted by DarrenSV650S

Wouldn't I just connect the inforad's wires to the control side of the relay and then the other side would switch the horns feed?

Kind of. The timer chip on the board needs a -ve going trigger, so depends on how the LED is driven, switched earth or switched +3v. If switched earth its straightforward, if +ve, then it needs a transistor added as an inverter.
Going to order the board and a mini siren and have a fiddle.