Son 28 dynamo / Busch&Muller IQ Cyo N Plus 60lux front / B&M 4D lite plus rear

[Skipper9999]

Son 28 dynamo / Busch&Muller IQ Cyo N Plus 60lux front / B&M 4D lite plus rear

I have the above set up on my bike and not sure if it's doing what it should?

For the early part of the bikes life I only had the front light fitted and it worked well. When at last I found some decent cable to run to the back I fitted that back on the bike.(it looks proper smart now).

Now which I think is obvious is that the front light is not quite as bright (or is that my mind) as it was ?

Now I am also sure its all AC power so the cable connection will not matter as long as the rear light is run from the front ?

The rear light has what looks like a switch on the top that does not do anything? is that a cable entry hole on the top and the switch is not a switch but in fact a connector?

What sort of brightness should I expect from the rear light?

I understand, I think that when I stop the bike the rear light will continue to glow ever so dimmer for an age unless I short out the 2 prongs on the outside of the light (but it still comes back on) ?

Any ideas out there ????

Skipper

 

[Rohloff_Brompton_Rider]

Have you run just a positive and used the frame as the return path? Like they used to do in the old days?

The setup you've listed should be bright as fark tbh.

 

[Skipper9999]

NO I ran a twin cable as I was to believe that the light did not earth through the mount (also its in the fender)

 

[Rohloff_Brompton_Rider]

Okey dokey...did you run them in series? I.e., positive from hub to front light out of the front light to the rear?

 

[Skipper9999]

I did not observe any polarity as I thought the set up was AC from the dyno.

I did swop the connectors over on the back light and it made no difference, if it was DC it would not have worked.

 

[Davidc]

That rear light is a standard B&M one, meeting the German standard, so it should carry on for at least 4 minutes of full brightness when you stop. It's a mudguard mounting unit so the polarity issue will depend on the mudguard material. I use Shimano dynamos which connect one side of the supply to the frame, the SON series AFAIK do not. However the CYO60 does, through the mounting bolt, so one pole of your supply is frame connected. The rear light mounting bolt is also a frame connection for one pole of the supply. Unless your mudguard is non-conducting plastic you need to ensure that the same pole is frame connected at both ends. Presumably you'll have used the switched supply wire from the CYO60 for the rear light, and the polarity is marked on the cable - look at the instruction booklet.

The supply is indeed AC, but once a frame connection is made it is frame referenced, so there is a polarity in the form of live and frame. In times past cycle dynamos came with only one connection for a wire, the bike frame was used for the other connection, and only a single wire had to be run along the bike.

The brightness of most dynamo rear lights is a bit less than the brighter battery ones, though there is a Herrman rack mount one which is up with them (I'm converting to those).

The brightness of the front light does go down when a rear is connected. The B&M lights are rated with a rear light connected. There is also a rating for the output with the full 3w fed to them with no rear connected (again look in the book, or on the B and M website).

Hope that's of some help.

 

[Rohloff_Brompton_Rider]

Iirc b and m are marked pos and neg. my b and m top flights are way bright and my fronts don't dim when the rear is connected, but they're led's.

 

[Rohloff_Brompton_Rider]

The two holes near the "switch" is to allow non stripped cables to be auto stripped. By this I mean, enter the cables thru the holes then flip the "switch" and they get stripped and held in place.

 

[Davidc]

Iirc b and m are marked pos and neg. my b and m top flights are way bright and my fronts don't dim when the rear is connected, but they're led's.

Some are, or more correctly they're marked + and - and those aren't positive and negative they're live and frame, and Herrman (Finnish company) are similar. They seem to reserve + and - mainly for the switched supplies coming from the front light. The - connection is the frame one. (Bizarrely the instructions for use of the lights with a battery pack say connect positive to frame. At that point I give up!)

 

[Rohloff_Brompton_Rider]

Actually zero volts is zero volts as the wave form produced is a half wave and doesn't drop below zero...hence being able to use voltage regulators not to fry bulbs by going too fast. As long as the lights are run in series and the same reference is used..I.e., zero is negative and plus 6v is on positive it should work fine. If the front is dimming when the rear is connected indicates a voltage drop somewhere or just poor connection to the rear light.

 

[Rohloff_Brompton_Rider]

Ok, try this....remove the front light from the bike but still connected to the pos and neg of the hub. Then disconnect the neg from the rear light but leave connected to the frame work. I know it sounds weird but iirc some hubs use the axle as ground. Now spin the wheel and see if it's sorted. If it is then you'll need to use nylon or similar insulation washers for the front light.

 

[Skipper9999]

The mudguards are plastic ....I will check connections tomorrow and report !!!!!
Thanks for help to here !!

 

[Davidc]

Actually zero volts is zero volts as the wave form produced is a half wave and doesn't drop below zero...hence being able to use voltage regulators not to fry bulbs by going too fast. As long as the lights are run in series and the same reference is used..I.e., zero is negative and plus 6v is on positive it should work fine. If the front is dimming when the rear is connected indicates a voltage drop somewhere or just poor connection to the rear light.

It's AC, goes positive for one half cycle and negative for the next relative to the frame. if there's no frame reference as from a SON the voltage is differential between the two wires. I suggest you look at the output on an oscilloscope if you want to see it.

Users, such as the ones supplied with Shimano dynamos, are AC regulators. Basically 2 zener diodes back-to-back.

You are wrong regarding the dimming of the front lamp. The type of generator used behaves as a constant current generator of 0.5A. With just a front lamp 0.5A goes to that lamp. With a rear lamp connected 0.43A goes to the front and 0.07A goes to the back. The reason it's a constant current source is simply the type of generator used. (You do clearly have to be going fast enough for the voltage output to rise to 6v for this to apply).

Finally, ALL bike dynamo lights operate with front and back in parallel. A series connection will never work.

I'm not discussing this further, as it's very basic physics which, if you don't like accepting it from me, you can look up.

 

[Davidc]

Ok, try this....remove the front light from the bike but still connected to the pos and neg of the hub. Then disconnect the neg from the rear light but leave connected to the frame work. I know it sounds weird but iirc some hubs use the axle as ground. Now spin the wheel and see if it's sorted. If it is then you'll need to use nylon or similar insulation washers for the front light.

Or more simply just swap the wires on the back light.

 

[Trickedem]

Skipper is this the light you have link

Have you wired the rear light up to the output cable from the front light?
I would also recommend using twin core cable, relying on the frame for an earth is unlikely to be reliable.

I have a similar set up although my light is this one It is very bright and lights up fully with just the smallest spin of the front wheel