diodes on relays

I am running 3 relays in my headlamp circuits. Would I need to put those diodes on them.
regards, Dereck

Peel had 3 relays in shell w/o need of diodes, after some brain and finger pain-strain to wire right. I made one big monkey fist ball connection of all common earth connections to simplify. Relays ended up in flat-ish trangluar array to fit with the extra wires. If ya settled on 3 relays then should work.

it was mentioned putting diodes on the ignition and charging circuit relays I think. Might be merit in that to protect the electronics.

Dereck,

It's my understanding that the diodes help to prevent current spike in the equipment they operate. I think it only applies to sensitive circuits. I do not believe a regular headlight or horn would fall into that category. Power to a Boyer or EI ignition might be something to consider. I know you have that LED headlight and perhaps there is a microprocessor in that crazy plug/fan. If it were mine I would not worry about it. If you are concerned about it they are easily available. just watch out because they are polarity sensitive. I know they operate slower (mico-seconds) then regular relays because the diode takes more tine to release the coil.

Pete

A diode really doesn't slow down a relay that I'm aware of, it just offers a path for the spike that is created when the magnetic field collapses when the relay is de-energized. You can add the diode externally or purchase relays with diodes built in. Relays with the internal diode are indeed polarity sensitive on the actuation coil.

The likely worst offender on the the whole bike is the starter relay on a MK3. I haven't heard of electronic ignition failure on those but maybe it's happening.

JimNH is absolutely correct. When the relay is turned off the collapsing coil can induce a current called inductive kickback. If necessary, a diode is placed across the coil terminals to short kickback and keep it from reaching any sensitive circuits. As pointed out by Pete, not necessary for horn or lights, but relays used for horns or lights will produce an inductive kickback. Using a diode across the coil terminals, even when not necessary, will do no harm. Obviously, the diode must be placed across the coil so it is reverse biased.

There is a basic primer on relays here:

http://www.physics.unlv.edu/~bill/PHYS483/relay.pdf

The 12 volts DC is positive in the illustration. For a positive ground system (conventional Norton) the diode connections would need to be reversed. For our purposes, disregard the transistor.

JimNH,

Slow is a relative term here. That spike that (might) be produced by the collapsing coil gets re-cycled back through the coil and holds the coil closed a little longer. In real world time that means nothing. In the world of high speed switches and mico processers it's probably like an ox cart vs. a nitro dragster. In these applications we would never see any difference. In my opinion anything it better then using these old switch clusters and 18 gauge wires.

Pete

Ta.

Huh, didn't know the diode relays existed or purpose but over kill on Cdo electronics or 10's of 1000's of us would of noticed by now. Audio equipment comes to mind on relay switch speed and EMF whiplash so I put a 5 amp stereo power filter on Peel ignition to help its brain keep the beat, yet it did not protect her LED lights becoming responsive ignition timing light pulsing with sparks and signal blinker rate which was a hoot at night at rally double takes with a non R plug installed but ran good to leave for home on.

DIY electronic upgrade stuff only a decade ago used to be only way to upgrade electric and electronics but nowadays there are many compact boxes that have multitude of whole range of cycle circuits each dampened relayed with circuit breaker protection to run light wire from it to switches and bigger wire to the active component. So those that just want to spend most time as happy pilot with the best function but not start a new side hobby, like me just cheated.

Btw way ya should know the reason for the smoke leaking out Lucas being a bad thing, if not replaced fast enough, smoke acts as lube for the electrons so they go dry heat up and seize w/o enough of it under voltage pressure. Universal principle of fluid dynamics like better lube going from 3 to 6 start oil pumps, same for 6 vs 12 volt. Waste of money for a jar of it when so easy to make your own electron lube. There are differing school of thot on whether to use the frame like a big chimney or run smaller dedicated duct work for returning electrons & the hidden smoke that carries them.

Ta.

The coolest one was shown me-we here a few yrs ago has labeled terminals and LED circuit lights. Peel's is more compact utilitarian Harley oriented ThunderHeart MIcro Harness Controller, here's ad but J&P Cycle catalog has more details and other units too.
http://www.amazon.com/Thunder-Heart-Per ... B000LQLBLU

Billet 6061 T-6 aluminum housing and 7ft. trim-to-fit wiring design is compact and easily hidden on custom motorcycles
Performs all fuse, relay (includes starter relay) and signal-canceling functions in one simple package
Provides multiple flasher combinations (signal canceling, hazard lights, running lights and turn signal) from one dual-filament bulb
Utilizes relays to distribute all power functions, thus eliminating the need to run large wires to all the switches
Can be used with micro switches

Ta.

Boy are you noisy, it goes over and behind the spinal tube base tap for oil temp sender hung in a woven mesh of what ever plastic crochet mats are made of. Maybe leather or rubbeer if can find right open light weave. Too complex a mounting location for me to figure out better like real mechanics and only half way figured out mudgaurd that don't foul the space. Sort of a hammick under rear seat base that will not be easy to spot with roaad going seat. Loom look like organic vessels so will be exposed just sewed up with th ick thread. Lucked out the big plug just fits through the big hole in R rear gasett so can feed main trunk of loom thru it yet still disconnet. Starter circuit was a sales point for Peel's air compressor which may be her biggest amp sucker. I'm preplexed about a battery and placement yet. Easy to delay project on new ideas, one was to cut spinal tube butt completely out and make a screw in battery tube but oil heat would cook em. I think that's Ludwigs tent pole stash. I've resolved my 2 brain split with 2 Commandos one only DIY hidden upgrades allowed like relays so glad I don't have to hunt spike dumping kind on her either. Will add my own stereo power separate from everything else but only needs a toggle switch I can swipe hand under seat for w/o looking before play La cucaracha or Dixie on arrival. Oh yeah almost all the switches the Micro Harrness can control will all be on one cluster on throttle side that also has a handy cable push-pull lever for compression release. Other side controls don't use electricity.

Ta.

micro box is only about cigarette pack size and half again bigger with the plug shoved most the way in. I did not mean to imply it'd fit in a head lamp just it relayed everything w/o relay clutter. Carry on the old ham radio way but blade terminal might foul the dodad lead. 1/2 size relays do matter in light shell.

Ta.

Ok always wondered if it mattered which way the blade faced. Getting beyond my need to know electrics now but here's ad that has size and cost comparison as not Peel photo of it yet.
http://www.jpcycles.com/wiring-harness- ... erformance

Deets55 said:

JimNH,

Slow is a relative term here. That spike that (might) be produced by the collapsing coil gets re-cycled back through the coil and holds the coil closed a little longer. In real world time that means nothing. In the world of high speed switches and mico processers it's probably like an ox cart vs. a nitro dragster. In these applications we would never see any difference. In my opinion anything it better then using these old switch clusters and 18 gauge wires.

Pete

Click to expand...

Pete,

I don't think any relay can be compared to an electronic switch based upon the inertia alone of a mechanical relay. I agree that if measured in tiny parts of a second, the diode may slow the contact break but, as you point out, it's meaningless in this application.

Happy Thanksgiving!

Jim

Another function of a diode for a relay or switch is to act as a snubber if the load is inductive like a solenoid....when power is cut to to the load the field collapses and generates a reverse polarity high voltage pulse, this can cause opening contacts to arc, damage upstream components, etc. (FWIW I recently learned this the hard way on my TR6 car, had a transistor blow in my DIY OD controller, adding a snubber diode across the OD solenoid prevented that as it shunts the reverse polarity spike to ground)