Is using diodes a good idea??

In trying to simplify my Commando electrics I wish to not use the stock master key-switch.

I have a very nice quality after market handle bar switch which I'm looking at using for the lights. But, it only has OFF - DIP - MAIN it does not have a dedicated feed to the tail and instrument lights (no idea why).

Before discarding the idea altogether, I wondered if it would be appropriate to take a feed to the tail light from both the main and dip, and fit diodes into the circuit to prevent reverse flow.

I am an electrical Luddite, so would like advice from those who are electrical savvy... Are diodes a good idea in this instance, or am I better off doing the job 'properly' which would mean using a different switch?

It will work fine but there's a little voltage drop through the diode; it shouldn't really be noticeable.

JimNH said:

It will work fine but there's a little voltage drop through the diode; it shouldn't really be noticeable.

Click to expand...

Thanks Jim. Can you advise what diodes I might buy for this application?

Why not have the switch operate relays? Then you can run anything you want off the relays.
Pete

Deets55 said:

Why not have the switch operate relays? Then you can run anything you want off the relays.
Pete

Click to expand...

Because I wouldn't really know where to start!

I don't think you have to worry about reverse current flow if your bike is wired the way I think it is. Connecting the tail light to both the main and dip terminals should not make for a problem since both are at the same potential. Could you show a schematic?

JimC said:

I don't think you have to worry about reverse current flow if your bike is wired the way I think it is. Connecting the tail light to both the main and dip terminals should not make for a problem since both are at the same potential. Could you show a schematic?

Click to expand...

My thinking is thus Jim: if I'm on main beam, the current will flow to the tail light, but if both main and dip are connected to the tail light, the current will also flow 'backwards' an illuminate the dip beam as well.

This would also happen vice-versa, so irrespective of whether I've selected main or dip, I'd always get both!

Hence, a diode in each feed to the tail light would stop this 'backwards' flow.

The bike is not wired at all yet, I've just started looking at doing this now.

Yes, diodes would work. Try a pair of 1N4001 (very common), and wire to work. That is, you'll need to see which way they need to go depending on whether positive or negative earth. As pointed out earlier, it'll drop your tail light brightness a bit, but only around 1 volt.

Nathan

You guys are right. I missed that. Little groggy, today. Didn't get to sleep until 4:00 AM. My apologies.

Why not have the switch operate relays? Then you can run anything you want off the relays

Eddie,
I hope I didn't come across the wrong way. If I did please accept my apology. Wasn't trying to be a smart ass, sometimes things come across wrong in text. I noticed it after re-reading the post.
Sincerely,
Pete

p.s. after thinking about what you need it appears to be a little more complicated than at first glance. Diodes will work.

Deets55 said:

Why not have the switch operate relays? Then you can run anything you want off the relays

Eddie,
I hope I didn't come across the wrong way. If I did please accept my apology. Wasn't trying to be a smart ass, sometimes things come across wrong in text. I noticed it after re-reading the post.
Sincerely,
Pete

p.s. after thinking about what you need it appears to be a little more complicated than at first glance. Diodes will work.

Click to expand...

Zero offence taken Pete.

It's just that when it comes to me and electrics, you have to talk slow, and loud, and repeat yourself a lot, even then there's a >50% chance you'll have lost me !!

Nater_Potater said:

Yes, diodes would work. Try a pair of 1N4001 (very common), and wire to work. That is, you'll need to see which way they need to go depending on whether positive or negative earth. As pointed out earlier, it'll drop your tail light brightness a bit, but only around 1 volt.

Nathan

Click to expand...

Thats great info Nathan, I Will do, thanks a lot.

Eddie,

Cool.

If you want I drew up something I think should work. It's two DPST relays and a fuse that will give you full battery voltage too you lights. A DPST relay has two sets of contacts that will allow you to keep your running lights separate from your Hi/Low beams. I am assuming you are going to use a simple on/off switch to control your ignition? I have not got around to setting up my photobucket but if you PM me you regular E-mail I can get it out to you. Won't be till tomorrow (East Coast time USA) I'm at work now.

Pete

Deets55 said:

Eddie,

Cool.

If you want I drew up something I think should work. It's two DPST relays and a fuse that will give you full battery voltage too you lights. A DPST relay has two sets of contacts that will allow you to keep your running lights separate from your Hi/Low beams. I am assuming you are going to use a simple on/off switch to control your ignition? I have not got around to setting up my photobucket but if you PM me you regular E-mail I can get it out to you. Won't be till tomorrow (East Coast time USA) I'm at work now.

Pete

Click to expand...

Thanks Pete. PM sent.

Fast Eddie said:

Deets55 said:

Why not have the switch operate relays? Then you can run anything you want off the relays.
Pete

Click to expand...

Because I wouldn't really know where to start!

Click to expand...

Then find out. Relays are the only answer when dealing with head lamps.

Fast Eddie said:

JimNH said:

It will work fine but there's a little voltage drop through the diode; it shouldn't really be noticeable.

Click to expand...

Thanks Jim. Can you advise what diodes I might buy for this application?

Click to expand...

As someone else pointed out, a 1N4001 is good. Here's some more I had in the electric drawer: 1N4007 which is probably about the same - a one amp diode; 1N5408 - a 3 amp diode; 6A6 -a 6 amp, probably way overkill for a tail lamp.

If you think the tail lamp is bright enough with the engine off, it'll be at least that bright with it running even with the slight voltage drop through the diode.

Fast Eddie said:

In trying to simplify my Commando electrics I wish to not use the stock master key-switch.

I have a very nice quality after market handle bar switch which I'm looking at using for the lights. But, it only has OFF - DIP - MAIN it does not have a dedicated feed to the tail and instrument lights (no idea why).


. Are diodes a good idea in this instance, or am I better off doing the job 'properly' which would mean using a different switch?

Click to expand...

If your OFF - DIP - MAIN switch has the OFF in the center position, your lights will go dark momentarily when switching beams....If OFF is not in center, then you could inadvertently turn lights off completely when switching beams....either way is not good.

Two switches will allow you to accomplish your goal without diodes. a single pole single throw for the LIGHTS function ( this powers tail & instrument and the dipper switch), and a single pole double throw for the MAIN/DIP function. The LIGHTS switch can be mounted in your dashboard or headlight shell, and the DIPPER on the handlebars.

Sorry, can't draw you a schematic at this time (no scanner available)


Slick

texasSlick said:

Fast Eddie said:

In trying to simplify my Commando electrics I wish to not use the stock master key-switch.

I have a very nice quality after market handle bar switch which I'm looking at using for the lights. But, it only has OFF - DIP - MAIN it does not have a dedicated feed to the tail and instrument lights (no idea why).


. Are diodes a good idea in this instance, or am I better off doing the job 'properly' which would mean using a different switch?

Click to expand...

If your OFF - DIP - MAIN switch has the OFF in the center position, your lights will go dark momentarily when switching beams....If OFF is not in center, then you could inadvertently turn lights off completely when switching beams....either way is not good.

Two switches will allow you to accomplish your goal without diodes. a single pole single throw for the LIGHTS function ( this powers tail & instrument and the dipper switch), and a single pole double throw for the MAIN/DIP function. The LIGHTS switch can be mounted in your dashboard or headlight shell, and the DIPPER on the handlebars.

Sorry, can't draw you a schematic at this time (no scanner available)


Slick

Click to expand...

Slick, funny you should mention that... there I was at midnight last night in the workshop just mulling things over with a beer... and I thought to myself "on a dark night, with cold gloved hands, when switching from main to dipped beam, it would be VERY easy to accidentally switch paased the dipped position and actually switch the lights OFF". Although this might only be for a split second, it is hardly ideal!

In other words, the latter scenario you mentioned!

I also have an excellent quality Domino switch 'in stock' that has seperate switches for on/off and main/dip. But its big and ugly so I didn't want to fit it.

However, looking more closely at function... and less closely at form... it is clearly the better option.

I'll still look into the fitting of relays though after the PM advice from Pete (thanks again Pete).

Eddie,
Glad to help.
Take a look at the MKIII switches. Rt switch lets you turn headlight off and on. Left switch is Hi- Lo (USA model). Problem is availability and $$$ and disc brake lever, etc. And you can use the E-start button as a kill switch when you power shift LOL
Pete

Using relays in lighting circuits is good practice, since not only does it allow you to fit the appropriate rated cable to reduce voltage drop at the lights, it also reduces the electrical load on your switch and extends the life of it. (carry a spare relay to cover most eventualities)

(ask who shoved high wattage bulbs in a company pool car he borrowed to do a local night rally, not realising that Mr Ford did not fit headlight relays on budget cars!......and burnt out the dip switch )

Putting diodes (that can be broken by vibration) into a 'safety critical' circuit on a motorcycle is bad practice. (1N4000 range are not desiged for use in 'rugged' environments, even if they are 1960s tech and typically survive quite well)

Honestly, it is also bad practice fitting a switch that has off between main and dip settings, as you have realised.

Like a lot of us however, I have coped with 'poor lighting', and the odd rider/driver induced 'total lack of lighting'.....for short periods....but I don't recommend it :roll:

I like the 2 switch idea, simply because it reduces the likelyhood of you being even momentarily without lighting. Even if a switch fails there is a work around to get dip on to get home.