Relay in a headlamp circuit

[ecurbruce]

When I have a relay in the headlamp circuit, does the relay contribute to the load of my system, and how can I determine how much load that is?
Thanks,
Bruce

[Sooners]

Yes, when energized, the relay coil becomes a load. The (I assume) 6 volt relay coil will draw a small current from your battery, to activate it.
When the relay is not being energized, it will not be a load on your battery.
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.

[ecurbruce]

Sooners says;
Yes, when energized, the relay coil becomes a load. The (I assume) 6 volt relay coil will draw a small current from your battery, to activate it.

Ok, thanks, and it's 12 volts, but the concept is the same.

Then the relay socket I'm using has a device on the back of it like a resistor in parallel with the relay coil wires. It's black and silver. What is it's function, and should I use it?

Bruce

[ducwiz]

The 6Volt relay definetly is a load to the system, when activated. But this load may not be so small as expected! This BOSCH relay here http://rb-aa.bosch.com/boaarocs/index.jsp;jsessionid=91665FA0E715B5726E3F4E82881768F2.sundoro2?ccat_id=30&prod_id=787&lang=en has 22 Ohms coil resistance, pullling an extra ~0.3 Amp at 7Volt in addition to the load (main lamp). This is equivalent to 2.2 Watts ! Modern relays (as the one offered by a sponsor of this forum ;o} ) are made with solid state switching elements instead of coils, armatures, yokes and contacts. This new technology operates with a negligible amount of power (milliWatts), therefore is highly recommended.

Hans

[DewCatTea-Bob]

[quote=ecurbruce ...
" When I have a relay in the headlamp circuit, does the relay contribute to the load of my system, "

____ Yes but, it's only supposed to be just a small-fraction of that of the light-bulb itself, added along-with.
So when any such relay is added, you can then certainly expect more/additional
total power-consumption ! - (Cuz also the light-itself is expected to then be able to draw some added-amount of extra-power, as well.)
__ Some relays employ a mechanical spring-loaded rocker-lever switch-setup, so that they just draw power only during the brief-moment of Hi/Low-activation, while other relay-types are always drawing some power (their-self), whenever the main-light circuit is powered-up.


" and how can I determine how much load that is? "

Or if you have a ampmeter, place it in serries with the coil and energize it and read its current value.

____ And then to determine your relay-unit's expected wattage-consumption, multiply your measured amp.reading x12 (or your actual/measured system-voltage). ...
So-if you were to happen to measure a rather reasonable .08-amps (flowing-through it's primary-circuit), then your relay-unit would be consuming near 1-watt.
__ It would be fairly interesting to learn what your r.unit actually does consume, so let us know if you find-out.



" Then the relay socket I'm using has a device on the back of it like a resistor in parallel with the relay coil wires. "

____ It seems like a 'resistor' would-not be in 'parallel', as that would only add to the relay-unit's overall power-drain. _ I'd more-so expect that piggy-back to be a 'condenser', (possibly used to absorb [collapsing-flux induced]- 'current-inertia', so as to protect the coil-relay's contact-points from arcing-damage).


" It's black and silver. What is it's function, and should I use it? "

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


Hopeful-Cheers,
-Bob

[Jordan]

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

[ecurbruce]

Bob says;
____ Got any pix to show of exactly what you've got ?
Bob, I'll post a photo tomorrow, 'cause my equipment is at my work...

I'd like to know more about this electronic relay that doesn't use much current to operate, anyone have more details on how it works? I'd consider converting to that, in my quest to conserve amperage.

[Jordan]

Suggest you do a search for Solid State Relay (product), Datasheets and Application Notes (literature).
There's tons of info available for electronic stuff.
Don't pay for it (sites that get it for nix then try to sell it), as it's basically advertising and free from manufacturers.
If you buy a CULayer product, you get it nicely mounted and packaged, and it's specifically made for Ducatis.

Jordan

[DewCatTea-Bob]

[quote=ecurbruce ...
" I'd like to know more about this electronic relay that doesn't use much current to operate, anyone have more details on how it works? "

____ Was-not your thread inspired by a recent-post of Jim's ? - http://www.culayer.com/Matchbox.htm



" I'd consider converting to that, in my quest to conserve amperage. "

____ So-then have you determined that your particular relay is-not the type which only consumes (rather minimal) power just during the moment it takes to activate it's rocker-switch ?


Hopeful-Cheers,
-Bob

[ducwiz]

Bob,

our "great repository of universal knowledge" tells us: https://en.wikipedia.org/wiki/Solid-state_relay

There are two versions - for DC loads made with MOSFET power transistors, for AC with SCRs (thyristors).

The DC version is what we need, in terms of reduced power consumption in particular.

A typical manufacturer is Croydom http://www.crydom.com/en/Products/Catalog/AdvancedWebPage.aspx?CategoryText1=PCB%20Mount&CategoryText2=DC%20Output&CategoryText3=CMX%20Series%20SIP%20SSR%20-%20Ratings%20to%2020A%20and%20200%20VDC%20-%20MOSFET%20output%20-%20DC%20control%20-%20Low%20on-state%20impedance&SBCatPage=

Hans