A B&M dyno light question

[andrew_s]

My old IQ fly stayed on until it discharged but my new IQ cyo can be turned off immediately.

Even so, the rear light will have its own standlight capacitor which won't turn off.

If you are lucky, might be able to find a reasonable non-standlight rear light, and the front light standlight may be able to supply power. Supernova springs to mind as a possibility.

[Bicycler]

I think I read somewhere (on here?) that unauthorised displaying of a light on a railway was prohibited by railway bylaws.

I've heard that too (but just red lights).

Tbh, I did recall the conversation being about just red lights

[NUKe]

Fairly stupid question perhaps. One of my lights is a Lyt N Plus, so it's manually switched. I never switch my dyno lights off normally but sometimes railway staff object to my lights being on. However, the switch on the back of the light doesn't switch the lights off. I assume this is a fault. Before I buy another one to replace it, am I right in thinking that if I move that switch the lights should turn off immediately?

And/or, any other recommendations for a similarly good commuting light, perhaps with a better quality switch? (The side visibility and integral reflector of the Lyt being more important in this case than the beam quality of, say, the Cyo.)

I have one of these and no its not a fault just the way its is built. My IQ cyo can be turned off but even that doesn't allow you to turn off the rear.


The problem with British rail is the red light rear and not the front. its illegal to show a red light within a station So you need either to be able to discharge the rear, non of which I am aware can be turned off, cover it or just use an LED rear and not a dynamo one when travelling. On the few occasion i travel by train my solution is to place an old sock over the rear whilst inside the station.

[drossall]

I wonder if there's a safety campaign on at present? I heard a member of railway staff asking a cyclist-passenger to turn off his rear light just the other day. Never come across it before.

My fixed has a standlight with no switch, so I'll be needing that plastic bag next time I go by train.

[MikeF]

This B&M rear light can be switched off. My Cyo front light has a simple rotary on/off switch. It's a non senso model. The Luxos has a push button on/off switch.

[fatboy]

My old IQ fly stayed on until it discharged but my new IQ cyo can be turned off immediately.

Even so, the rear light will have its own standlight capacitor which won't turn off.

If you are lucky, might be able to find a reasonable non-standlight rear light, and the front light standlight may be able to supply power. Supernova springs to mind as a possibility.

And I have a b&m rear light with the shortable contacts too!

[mike_dowler]

I was half-heartedly asked to turn off my rear light the other morning. I told him that it doesn't switch off, until the battery goes out. He asked if I could wait til the battery went out. I said no, and went up to the platform.

[edocaster]

The 'switching off dynamo standlights' question gave me a 'huh?' moment too when I first got my (Axa and B&M) lights. It does look like only a handful of the (mostly more expensive) lights have what I assumed was a basic feature.

But when I built my own light, I decided to leave out an off switch for the standlight too. Reading around various forums, it appears that this feature is not completely trivial to implement in the most basic standlight circuits. A simple off switch in the standlight circuit risks one forgetting to switch the standlight back on when setting off (something you wouldn't notice until the first stop).

The solution is a dual-pole switch which gangs the input switch with the standlight switch. That way, you know instantly whether light and standlight are on or off. More fancy would be three positions: Input and standlight on, input off and standlight on, all off.

I don't know how the B&M lights which do allow disabling the standlight work. I suspect they *don't* discharge the capacitor per se, as the supercaps tend to be (has anyone opened to check?) coin types like this: http://uk.mouser.com/ProductDetail/Pana ... d0n8NmY%3d and they're not really designed for discharge rates beyond the 'mA range'. They're already being overdriven, but expecting them to discharge in a second might be too much. I suspect it just triggers a switch which disconnects the standlight, and B&M have a way of re-engaging the standlight as soon as the bike moves and current flows, via some kind of latching switch circuit.

[MikeF]

I don't know how the B&M lights which do allow disabling the standlight work. I suspect they *don't* discharge the capacitor per se, as the supercaps tend to be (has anyone opened to check?) coin types like this: http://uk.mouser.com/ProductDetail/Pana ... d0n8NmY%3d and they're not really designed for discharge rates beyond the 'mA range'. They're already being overdriven, but expecting them to discharge in a second might be too much. I suspect it just triggers a switch which disconnects the standlight, and B&M have a way of re-engaging the standlight as soon as the bike moves and current flows, via some kind of latching switch circuit.

You're right; the switches on B&M lights do not discharge the capacitors for the standlights. On the front lights the on/off switch turns the standlight and connection to the "dynamo" on or off without affecting the charge in the capacitor. On the rear light the switch turns the light off, but does not turn it on, also without discharging the capacitor. As you note there seems to be a very sensitive latching circuit which turns the rear light on as soon as it receives a slight input/trigger from the "dynamo".

The capacitors retain their charge for days - maybe weeks. Quite amazing!

You're also right in that simply shorting the capacitors is likely to damage them. They should be discharged through a resistor.

Useful supplier link.

[stewartpratt]

This B&M rear light can be switched off. My Cyo front light has a simple rotary on/off switch. It's a non senso model. The Luxos has a push button on/off switch.

Oh. As it happens I have all of those - though none of them are on my commuter. Haven't fitted the Topline yet (no 50mm mount on my rack).

[The Mechanic]

This B&M rear light can be switched off. My Cyo front light has a simple rotary on/off switch. It's a non senso model. The Luxos has a push button on/off switch.

Oh. As it happens I have all of those - though none of them are on my commuter. Haven't fitted the Topline yet (no 50mm mount on my rack).

I have a Topline on my audax bike and it does indeed have a switch to discharge the standlight. I guess it is a case or cheaper lights have less features. My IQ Cyo can be switched completely off by the rotary switch on the back of the light.