The Exposure redeye runs off the output from a Revo etc. The Revo output can also be used for charging. I assume the Revo converts for DC to AC (think that's the right way around).
So can I run the redeye from a power bank?
That way I can just swap the rear light between the dynamo and non dynamo bikes.

Dynamo output is AC as bike dynamos are actually alternators and not dynamos but never mind that. So, your Revo will run AC. I assume if you want to run the output for charging you'll need to first pass the current through some kind of rectifier / regulator (charging box) or do you? There may be diodes built into the Revo to handle this but I don't know.

FA help I know.

I just plugged the Redeye into the port of my MAXX-D and it worked fine.

LED’s work with dc as they are as the name implies a type of diode. I would imagine it would be fine with a typical power bank if you can find a connector, an exposure usb charging lead and barrel-barrel adapter as used to charge the exposure support cells might work. I’d ping exposure an email just to be sure though.

Exposure lights need special cable to do the USB charging, think it’s called a boost cable or some such. This is not compatible with the Revo afaik

Make sure the polarity is correct when you do this !

LED drivers really dont like it being reversed.
Check the output from the revo with a multimeter to see what it is and make sure you match it.[ will also confirm its DC which i assume it is]

I was thinking if I used an exposure usb charge lead with a piggyback connector connected to the red-eye cable either connected to a power bank or to the k-lite usb charger?

LED’s work with dc

Is that true of all led Steve? If so, the the Revo must feature internal diodes to covert the dynamo output.

Bearbonesnorm wrote: ↑Thu Nov 07, 2019 9:07 pm

LED’s work with dc

Is that true of all led Steve? If so, the the Revo must feature internal diodes to covert the dynamo output.

I believe so, if you reverse the battery polarity to a LED it won’t light as current can only flow one way, it’s possible that pairs of led’s are bridged but in reversed polarity to maximise output.

If you are trying to charge a device with the Revo output my advice is don't. It will be very current limited, and unlikely to be very clean (noisy DC at best). You'll be lucky to get 100mA out of it, and overloading it is likely to end up with a phone call to Exposure.

You are much better off using a proper rectifier and current controlled device like the cycle2charge and ewerk etc.

And then re-reading your post yes, you can run a redeye from a power bank

You May have hit the nail on the head there, perhaps the revo uses the led’s as a simple half wave rectifier? Hence poor performance.

If it helps the OP I’ve just tried my micro redeye
Connected to the support cell via the support cell charger adaptor, works a treat

To be honest by the time you’re sourced the cables and adapter you may be better off getting another rear light, if you have a joystick that would run it I think.

Thanks everyone.
Good news is it will work and I've got a joystick.
I'll get the red-eye now

Bearbonesnorm wrote: ↑Thu Nov 07, 2019 9:07 pm

LED’s work with dc

Is that true of all led Steve? If so, the the Revo must feature internal diodes to covert the dynamo output.

Yup they do, partly why they cost so much. A redeye will work off any 6v supply

Diodes are cheap as chips, actually a lot cheaper, can’t see why they should increase the cost by any great amount. Diodes act as one way valves, if you were to connect one to an AC supply it would flash at the Hz of the AC, the wave form of the output would look like a typical AC output with one half cut off,
A simple bridge rectifier uses four diodes to utilise the other half of the AC wave while flipping the polarity, the result is a lumpy DC output, a capacitor can provide some smoothing.

Cost £2? Ish, it won’t be a nice DC output, but will run our light emitting diode in a flicker free fashion.
At work our chain hoists use bridge rectifiers to feed DC magnetic load brakes, some use AC brakes which rattle away at 50Hz

I have used the Revo for years and recently decided that I might get an exposure rear light as well. I did weigh up the Redeye as an option but I really don't like that the wire can't unplug from the light. Anywhere I wouldn't leave the Revo on the bike I doubt I wouldn't want to leave the red-eye on either. PITA to have to take the wire off as well. Also doesn't give me any option to use the light on the helmet if I decide that was preferable.

I decided for my use that the Tracer would be better. Not got one yet but fairly close to taking the plunge.

Very good lights I’ve been told it’s slightly too good for group rides

You can think of a diode as a one-way valve but it's more like a barrage in a river, under normal conditions the current flows downstream but if the river level downstream is high enough then you can get reverse flow.

In a diode this is called the breakdown voltage and is typically much higher than the normal operating voltage. So if you put a diode into a 6V AC circuit (as is typical output from an alternator/dynamo) then there's unlikely to be damage, they are sensitive to excess current being applied. The same applies if you put a diode into a DC circuit "the wrong way round". The effect due to the breakdown voltage is temporary so reverse the voltage and the device will work as normal. There is a much higher voltage that will cause the device to burn out, mainly due to the effects of heat.

composite wrote: ↑Fri Nov 08, 2019 12:55 am I decided for my use that the Tracer would be better. Not got one yet but fairly close to taking the plunge.

I've got a TraceR, great light but I don't get the run time they suggest. On the BB300 with it on the 24hr setting it went flat before morning. I put it on late afternoon so I think I got about 14 hrs run time? It was also on for the ride to the start but that took less than an hour. It is bright even on the lowest setting and I like the fact that if it's foggy I can turn it up to the highest setting to make me more visible.

The redeye is also a great light and very bright. You could cut the wire close to the light and fit another plug and socket to make it easy to remove? I've never worried about mine being stolen, the wire is cable-tied to the brake line along the underside of the top tube so they'd have to cut them off to get it off.

Ah, it really is winter. The physics-dorks come out to rattle on about bloody lights, bit like the inverse of the first swallow of spring or whatnot

I was always a biologist so physics waffle goes over my head but weirdly I still quite enjoy reading it. I do love bright, small, lightweight effective lights though (compared to the ancient Cateye NiMH I started night riding with) and so shouldn't be too cruel to you all

I really like my Redeye (bigger one, not the micro). It's almost daftly bright but I like the certainty (quite possibly unfounded or misplaced) that drivers will see me from behind. Edit - for me that offsets the slight inconvenience of the cable.

sean_iow wrote: ↑Fri Nov 08, 2019 9:26 am

composite wrote: ↑Fri Nov 08, 2019 12:55 am I decided for my use that the Tracer would be better. Not got one yet but fairly close to taking the plunge.

The redeye is also a great light and very bright. You could cut the wire close to the light and fit another plug and socket to make it easy to remove? I've never worried about mine being stolen, the wire is cable-tied to the brake line along the underside of the top tube so they'd have to cut them off to get it off.

Hmmm OK that is a really good point I didn't think about to be fair. The places that I might leave the bike, outside a shop or cafe on an Audax for instance where I could easily remove the Revo, a cabled tied light will almost certainly be fine. Even where I park for my commute is a keypad access bike rack at work so should be fine there as well. Putting a new plug on the wire would give other options for easily moving between bikes. Although I guess Exposure doesn't sell the cable separately as it's not meant to be unplugged like the dynamo to Revo cable.

I’d second Sean on that point.
On of my Redeye’s sits on my commuter permanently. The cable is zip tied down and the light has stayed un-nicked for two years,

If you were to fit another plug to the redeye I can highly recommend the SON coax plugs and connectors

so are the sinewave ones but you need to be able to solder -sjs cycles£4 for a set iirc

They slide in really easily with little resistance [ I swap mine between bikes ]