Relay in a headlamp circuit

[ecurbruce]

Bob says;
____ Got any pix to show of exactly what you've got ?

The photo is of the back side of relay socket, black and silver device in parallel with coil side of relay. I clipped one end of device, as this device is not used with the automotive headlamp relay I used...

Bob says;
____ Was-not your thread inspired by a recent-post of Jim's ? - http://www.culayer.com/Matchbox.htm
Yes, I am inspired by Jim's posting, and now I want to know more, and convert to electronic relays.

Sooners says;
If you don't have any specs, or the relay doesn't have a "VA" number printed on it, you can do a couple things. If you have a ohmmeter, disconnect wires from the relay coil and measure the resistance of the coil. It's current load will then be the battery voltage divided by that resistance value. Or if you have a ampmeter, place it in serries with the coil and energize it and read its current value.
So my relay resistance is 73.8
Divide by 12.5 is 5.9 amps,
Thats as high as my h-lamp bulb, I'll not be using that!

Bruce

[DewCatTea-Bob]

[quote=ecurbruce ...
" black and silver device in parallel with coil side of relay. "

____ That's obviously a diode, (if you had stated that it was black with a white-stripe at one end, then I would've known without seeing your picture of it),,
so it seems that Jordan was correct !


" I clipped one end of device, "

____ You probably ought-not have done that.



" Yes, I am inspired by Jim's posting, and now I want to know more, and convert to electronic relays. "

____ Those relay types probably consume well-under 100mA, (and perform their switching-task in a rather silent manor). _ But your relay may be the mechanical-type which (normally) consumes no power at all...
You could check to determine-so, by (quickly) activating it once (on & off ... whilst closely-listening),, if you then hear it perform a DOUBLE-click -(sounding like 'click,clack'),, then your relay is the simple/cheaper (magnetically held-closed) type which constantly draws power-juice whenever the headlight-circuit is turned-on, (as it's magnetic-coil always has to overpower it's return-spring -[which is depended-upon to break the circuit (thus-then making the 'clack' noise)] ).
However (during it's on/off activation-test), if you merely hear just a rather simple SINGLE-click only, (even-if when ya completely cut-off it's power-source) and don't hear any following 'clack',, then your relay-unit should be the rocker-spring type which only draws it's required power merely during just the brief-moment of being activated. _ This relay-type uses a spring (instead of magnetism) to keep it's contact-points held-closed (and therefore kept 'closed-circuit' even after the activating-power is cut-off). _ Then the next time the relay-switch is activated, (then switching-over from high to low, or low to high), it will click only a single-click, again, (and then leave the 2nd.circuit closed).
This more complex relay-type is usually a bit larger & heavier (and usually has a relatively shorter [switching]- life-span, due to it's added internal-complexity, [and naturally usually finally get-stuck in the low-beam setting] ).
____ I think I know what you may have in mind for the use of a power-relay for YOUR merely SINGLE-filament headlight.



" So my relay resistance is 73.8
Divide by 12.5 is 5.9 amps,
I'll not be using that! "

____ You did your math backwards... The correct result-figure is .17-amps ! - (About double the 80mA which I had expected.)
That means that your relay-itself would consume about 2-watts. _ (Which would be a relatively small price to pay for the wattage-SAVINGs you could possibly get, if you're planning to actually do that which I suspect you're considering.)


Hopeful-Cheers,
DCT-Bob

[ecurbruce]

Bob says;
____ You did your math backwards... The correct result-figure is .17-amps ! - (About double what I had expected.)

See-there, that's how I get myself in trouble...LOL
That relay works as is on the ground side of a halogen HB3 60 watt bulb, but I might like to convert to SSR anyway.

Bruce

[DewCatTea-Bob]

____ You managed to get-around to placing your response-post before I had completely finished my previous-post, so I'll now use THIS-post to finish my thoughts which I was going to get-to before...

[quote=ecurbruce
" That relay works as is on the ground side of a halogen HB3 60 watt bulb, but I might like to convert to SSR anyway. "

____ I hadn't realized that you've already been actually using your relay with your single-filament headlight. _ It doesn't seem it would've been of much good-use if you weren't using it to divert it's current-demand away-from your Hi/Low-switch & it's extended-wiring.
__ So I now no-longer think I know what you've had in mind for the use of such a relay... So what exactly IS your thinking for needing a headlight-relay (when your single-filament bulb doesn't make-use of a Hi/Low-switch and-thus can get it's power DIRECTLY from the light-switch just as well) ? _ Are you thinking that your main-light's switch is also not up-to-par with that of the relay's switching-contacts ? _ If your 60w.bulb was still a 6v.version, then I'd agree that the stock headlight-switch is probably not up-to handing the current-demand (of such a powerful 6v.bulb), as well as the relay could,, but your 12v/60w.bulb only demands the same amount of current as a 6v/30w.bulb, (which the stock main light-switch is well up-to) !
So therefore, there's no BIG advantage for making-use of a headlight-relay, unless,,
unless your intended headlight-circuit entails making-use of a 12-gauge power-wire to DIRECTLY-connect your headlight-bulb all the way back-to your battery's pos.post. _ As THEN, there could be some worthwhile functional-use for such a power-relay !
__ But otherwise, I'm back to wondering why YOU (with your SINGLE-filament light-bulb) wish to employ a Hi/Low headlight-relay...
I was thinking that you were exploring the notion of using such a circuit-setup so as to provide your single-filament light with the option of alternate brightness selections, with your main end-goal possibly being to be able to cut-down your headlight's rather high power-demand, for whenever you happen to need to run at lower eng.revs for an extended-time, (so as to then conserve battery-discharging).
Is that a function which you were actually considering ? _ Or did you have some-other idea in-mind ?


Enlightening-Cheers,
-Bob

[ecurbruce]

Bob,
My headlamp circuit has a dedicated 12 gauge wire from the battery to to bulb, the single pole on-off relay from the negative side of bulb, then grounded through a 12 gauge ground wire from the headlamp housing to the battery negative, fused at the battery. It seemed like a good idea at the time. I don't yet have a high-low switch, but I will at some point- it's always a work in progress. Then I'll need a two filament bulb and a different relay.

I also used a relay between the alternator and the battery positive side, as a straight through switch. The activating coil side of that relay circuit goes from the positive battery (fused), through the relay, to the keyed ignition switch in headlamp housing, then to ground. So the key only operates the relay.(the key switch also connects the ignition).this also seemed like a good idea at the time???



Bruce

[ecurbruce]

Jordan says;
Or a flyback diode, often used when there's a coil to prevent arcing at points?

Jordan or Bob, do you think I should reconnect that diode to the back of relay socket for the headlamp circuit?

Bruce

[DewCatTea-Bob]

[quote=ecurbruce ...
" My headlamp circuit has a dedicated 12 gauge wire from the battery to to bulb, the single pole on-off relay from the negative side of bulb, then grounded through a 12 gauge ground wire from the headlamp housing to the battery negative, fused at the battery. It seemed like a good idea at the time. "

____ Well indeed SO, as that's the best-way to take maximum-advantage of a headlight/relay-circuit !
So that which you've wired-up & done, thus-then allows your 60w.light to draw-power as much as it possibly can !
__ How do you activate your relay ? _ With the stock light-switch ?



" I don't yet have a high-low switch, but I will at some point-
Then I'll need a two filament bulb and a different relay. "

____ To attain true Hi/Low headlight-beams, that would then of-course have-to be the case.
__ However, with your relay & light-switch, you could choose to have a high/low-intensity headlight-option !
That could be done by connecting your light-switch's output directly-to your single-filament light-bulb through a rather thin 18-gauge wire along-with a resistor in-line with it, thus-then providing you with a LOW-intensity headlight-circuit, (as well as less load/drain on your battery).
And then to also keep available your high-intensity headlight-option, you'd retain-in-place your present relay-circuit setup, in PARALLEL with the suggested added resistor-circuit. _ That way, your headlight could be kept dimmer UNTIL you let your relay-circuit ALSO pass-on power to your light-bulb as well !
__ The suggested resistor-circuit would use a pair of 1-ohm power-resistors (rated 5 to 10 watts) connected in parallel (so as to yield just .5-ohm).
The result of that added resistor-circuit (in series with your light-bulb) would reduce the light-filament load to (about*) 45-watts (+/- 3.5-watts).
(* It's not very possible to normally-calculate the EXACT reduced wattage-amount because as the filament passes less current, it then runs cooler and-so it's resistance-value thus-then becomes less [than at normal-operation]. _ And-so without actually measuring the filament's altered-resistance, I can only [fairly closely] estimate-calculate the power which it-itself consumes.)

I also used a relay between the alternator and the battery positive side, as a straight through switch. The activating coil side of that relay circuit goes from the positive battery (fused), through the relay, to the keyed ignition switch in headlamp housing, then to ground. So the key only operates the relay.
this also seemed like a good idea at the time???

____ This seems like an idea I've never thought-of...


" I also used a relay between the alternator and the battery positive side, as a straight through switch. "

____ I can't seem to make-sense of what you're actually meaning to convey with that wording. _ Can you please try-again in other-words ?



" The activating coil side of that relay circuit goes from the positive battery (fused), through the relay, to the keyed ignition switch in headlamp housing, then to ground. So the key only operates the relay.
this also seemed like a good idea at the time??? "

____ If I'm understanding everything-above correctly, the purpose of THAT-relay in that electrical-location, is to keep the ign.switch from having to carry the normal system-power,, which would indeed be a good-idea, if your headlight was still getting all it's power through the ign.switch, (as like stock). _ But with the headlight's current-draw already diverted away-from the ign.switch,, the remaining current-demand (of the REST of the load-system) through the ign.switch, actually ought-not be of any real concern (unless your stock ign.switch has been slightly burned-up a bit) !
__ Am I missing anything ? ... Is there some actual-concern for further lightening-up your ign.switch's load (even after the headlight-load has been taken off it's back) ?


Enlightening-Cheers,
DCT-Bob

[Jordan]

do you think I should reconnect that diode to the back of relay socket for the headlamp circuit?

Bruce

Yes

[Jordan]

" I also used a relay between the alternator and the battery positive side, as a straight through switch. The activating coil side of that relay circuit goes from the positive battery (fused), through the relay, to the keyed ignition switch in headlamp housing, then to ground. So the key only operates the relay.(the key switch also connects the ignition).this also seemed like a good idea at the time??? "

____ This seems like an idea I've never thought of...

You lose the ability to isolate the battery if the relay fails "on". I guess you could put a separate isolation switch in the high current circuit, but would you remember that in a short circuit emergency?

Jordan

[ecurbruce]

" I also used a relay between the alternator and the battery positive side, as a straight through switch. "

____ I can't seem to make-sense of what you're actually meaning to convey with that wording. _ Can you please try-again in other-words ? "

I'm just saying, where some relays are used to ground a device, this one is used to interrupt the circuit between two devices.


Bob says:

__ Am I missing something ?

Yea, what's missing is the voltage regulator, the relay is between the voltage regulator and the battery.
I'm describing this by memory, I don't have the bike in front of me right now, so lets pick up this later, when I can look at it , and not make any more mistakes...

Bruce