Dynamo Woes

My bike is equipped with a Schmidt SON hub dynamo, Lumotec Oval Plus front light and Dtoplight Plus
rear light.

Last night, my front bulb blew. Fortunately, I had a spare. Unfortunately, it appears that when the
front bulb blew the entire voltage from the dynamo went through the back light, blowing the LED. And
it appears that this is not designed to be replaced - looks like the unit's knackered.

I had thought that both lights had overvoltage protection. But I just downloaded the Dtoplight
manual from http://www.bumm.de , and it specifies that this is not for hub dynamos. Bummer.

So, can anyone recommend a rear dynamo light with standlight that won't blow if the front bulb
blows, or at least one where I can easily replace the bulb/LED if necessary?

--
Danny Colyer (remove safety to reply) ( http://www.juggler.net/danny ) Recumbent cycle page:
http://www.speedy5.freeserve.co.uk/recumbents/ "He who dares not offend cannot be honest." -
Thomas Paine

 

Tue, 4 Mar 2003 23:24:05 -0000, Danny Colyer:

>
>I had thought that both lights had overvoltage protection. But I just downloaded the Dtoplight
>manual from http://www.bumm.de , and it specifies that this is not for hub dynamos. Bummer.

There was an older series of DToplight with bad (no ?) overvoltage protection. Write to "info at
bumm de" and ask politely what to do. They usually offer a replacement PCB-insert with LED and
electronics for free...

But usually the supressor diode in the headlamp should provide enough protection for the back light.
Do you have the Oval Plus with the toggle switch or the Oval Senso Plus with the sliding switch?

Andreas

 

Andreas Oehler suggested:
> Write to "info at bumm de" and ask politely what to do. They usually offer a replacement
> PCB-insert with LED and electronics for free...

Thanks, I'll do that.

> But usually the supressor diode in the headlamp should provide enough protection for the back
> light. Do you have the Oval Plus with the toggle switch or the Oval Senso Plus with the
> sliding switch?

The latter.

--
Danny Colyer (remove safety to reply) ( http://www.juggler.net/danny ) Recumbent cycle page:
http://www.speedy5.freeserve.co.uk/recumbents/ "He who dares not offend cannot be honest." -
Thomas Paine

 

On Tue, 4 Mar 2003 23:24:05 -0000, "Danny Colyer" <[email protected]> wrote:

>My bike is equipped with a Schmidt SON hub dynamo, Lumotec Oval Plus front light and Dtoplight Plus
>rear light.
>
>Last night, my front bulb blew. Fortunately, I had a spare. Unfortunately, it appears that when the
>front bulb blew the entire voltage from the dynamo went through the back light, blowing the LED.
>And it appears that this is not designed to be replaced - looks like the unit's knackered.
>
>

since its knackered you might try taking it apart ( they're not well made) and soldering a
new led in.

 

Wed, 5 Mar 2003 19:22:26 -0000, Danny Colyer:

>> But usually the supressor diode in the headlamp should provide enough protection for the back
>> light. Do you have the Oval Plus with the toggle switch or the Oval Senso Plus with the sliding
>> switch?
>
>The latter.

Look what happend to the supressor diode in the headlamp! Earlier Senso's had the diode mounted on
the PCB inside (bad place - poor cooling!): It is a black cylindrical item on the upper edge of the
board. Is it soldered properly?

On newer models the diode sits in the headlamp base. You should see one tinned wire clamped under
the Phillips screw.

Andreas

 

On Tue, 4 Mar 2003 23:24:05 -0000, "Danny Colyer" <[email protected]> wrote:

>My bike is equipped with a Schmidt SON hub dynamo, Lumotec Oval Plus front light and Dtoplight Plus
>rear light.
>
>I had thought that both lights had overvoltage protection. But I just downloaded the Dtoplight
>manual from http://www.bumm.de , and it specifies that this is not for hub dynamos. Bummer.
>

I do not have the Lumotec Oval - I just have the standard Lumotec. I found that the regulator can
become disconnected. It is just crimped to the copper conductors in the lower part of the
headlamp and these crimps can come loose. See if you can make sure the connections to the
regulator are sound.

I do not know of a simple way to test if the regulator is working - I used an oscilloscope at work
and could see when the regulator was restricting the voltage to about 20V peak tp peak. Before it
was fixed, the peak to peak voltage could get as high as 24V.

John T Remove the singers of Spam before replying

 

[email protected] suggested:
> since its knackered you might try taking it apart ( they're not well made) and soldering a
> new led in.

I probably will. But I think it's a safe bet that it won't be waterproof if I manage to get it back
together again, so ultimately I'll still be looking at a replacement.

--
Danny Colyer (remove safety to reply) ( http://www.juggler.net/danny ) Recumbent cycle page:
http://www.speedy5.freeserve.co.uk/recumbents/ "He who dares not offend cannot be honest." -
Thomas Paine

 

Andreas Oehler wrote:
> Look what happend to the supressor diode in the headlamp! Earlier Senso's had the diode mounted on
> the PCB inside (bad place - poor cooling!): It is a black cylindrical item on the upper edge of
> the board. Is it soldered properly?

I can see no black cylindrical items on the PCB (or anywhere else for that matter). The lamp is 2
years old, FWIW. I bought the bike with the lights ready fitted and I can't say I've ever looked at
it in great detail.

> On newer models the diode sits in the headlamp base. You should see one tinned wire clamped under
> the Phillips screw.

I can find 4 Phillips screws. One at the top left and one at the bottom right of the PCB. These have
wires connecting to the front of the lamp which presumably supply power to the standlight. One just
behind the connection for the wires that go to the back light. The fourth screws the lamp to the
bracket, and is just below the wires from the dynamo.

I can see that the wires from the dynamo go behind the PCB, so I wondered if the suppressor diode
might be back there. I was reluctant to dismantle the lamp, since it was working, but curiosity got
the better of me and I couldn't see any black cylindrical items on the back either.

(Screwing the PCB back in place was as much of a challenge as I expected, but I took photos so I
shouldn't need to unscrew it again if I want to see what it looks like at the back).

--
Danny Colyer (remove safety to reply) ( http://www.juggler.net/danny ) Recumbent cycle page:
http://www.speedy5.freeserve.co.uk/recumbents/ "He who dares not offend cannot be honest." -
Thomas Paine

 

Danny Colyer <[email protected]> wrote:
>So, can anyone recommend a rear dynamo light with standlight that won't blow if the front bulb
>blows, or at least one where I can easily replace the bulb/LED if necessary?

While we're at it - having discovered a failure mode that took out both my battery headlights on
Wednesday, I have decided to bite the bullet and get a SON. I've got a no-name rear LED bulb
replacement (ie, one of those LEDs with a bulb base) because the rear reflector on my mudguard is
intended to accomodate a rear bulb; am I right in thinking the currently favoured headlight if you
don't want a standlight is the Bisy?
--
David Damerell <[email protected]> Kill the tomato!

 

Thu, 6 Mar 2003 23:00:08 -0000, Danny Colyer:

>Andreas Oehler wrote:
>> Look what happend to the supressor diode in the headlamp! Earlier Senso's had the diode mounted
>> on the PCB inside (bad place - poor cooling!): It is a black cylindrical item on the upper edge
>> of the board. Is it soldered properly?
>
>I can see no black cylindrical items on the PCB (or anywhere else for that matter). The lamp is 2
>years old, FWIW.

Than it should be on the upper edge at the front of the PCB. It happens that the diode gets so hot,
that it "desolders" itslef. You should see at least two tinned and drilled round pads on the PCB,
where the diode has been...
>> On newer models the diode sits in the headlamp base. You should see one tinned wire clamped under
>> the Phillips screw.
>
>I can find 4 Phillips screws. One at the top left and one at the bottom right of the PCB. These
>have wires connecting to the front of the lamp which presumably supply power to the standlight. One
>just behind the connection for the wires that go to the back light. The fourth screws the lamp to
>the bracket, and is just below the wires from the dynamo.

Sorry for beeing unclear. I meant the big screw near the connectors for the rear ligh. Can you see a
single wire coming from the inside of the lamp clamped under this screw head? Around 2 years ago the
manufacturer started to move the diode from the PCB to this better cooled location.

Andreas

 

Andreas Oehler wrote:
> You should see at least two tinned and drilled round pads on the PCB, where the diode has been...

The closest I could find was the bit circled here:
http://www.speedy5.freeserve.co.uk/lumotecfront1.jpg

Might that be where the diode should be?

But that's more on the back of the PCB - unfortunately my best picture of the back is more poorly
focussed than the picture of the front (the bit that was circled in the first picture is at the
bottom right in this picture): http://www.speedy5.freeserve.co.uk/lumotecback1.jpg

> Sorry for beeing unclear. I meant the big screw near the connectors for the rear ligh. Can you see
> a single wire coming from the inside of the lamp clamped under this screw head?

Thanks for the clarification. No, there's not a wire there. The screw has a copper contact
underneath it, which would be used when connecting 2 front lights in series, but no wire.

> Around 2 years ago the manufacturer started to move the diode from the PCB to this better cooled
> location.

I've probably got the older version, then. I took delivery of the bike, with lights ready fitted, in
January 2001.

--
Danny Colyer (remove safety to reply) ( http://www.juggler.net/danny ) Recumbent cycle page:
http://www.speedy5.freeserve.co.uk/recumbents/ "He who dares not offend cannot be honest." -
Thomas Paine

 

Fri, 7 Mar 2003 22:21:29 -0000, Danny Colyer:

>
>The closest I could find was the bit circled here:
>http://www.speedy5.freeserve.co.uk/lumotecfront1.jpg
>
>Might that be where the diode should be?
>
>But that's more on the back of the PCB - unfortunately my best picture of the back is more poorly
>focussed than the picture of the front (the bit that was circled in the first picture is at the
>bottom right in this picture): http://www.speedy5.freeserve.co.uk/lumotecback1.jpg

Looks like one of the very early versions of the PCB... The diode seems to be the thing you marked
with the red circle. The pictures are not perfectly sharp but it seems as if the diode has
desoldered and one lead isnt connected anymore. It should be positioned in parallel to the border of
the PCB but now it moved (by heat and vibration) to a diagonal position.

You can solder it back in, but this wouldn't really solve the problem. If the next bulb dies and you
continue to ride the bike with the light (automagically switched on), the diode will desolder
again... I would recommend to take the diode out of the lamp housing and solder it between the
connectors at the base of the lamp. There it is cooled by the airstream.

Andreas

 

Andreas Oehler wrote:
> I would recommend to take the diode out of the lamp housing and solder it between the connectors
> at the base of the lamp. There it is cooled by the airstream.

Thanks for the advice. I'll take another look and give that a go. I think I'll wait a few weeks,
though, because by then I won't actually need lights and I can easily take my time, having several
goes over several evenings if necessary (soldering never seems to go right first time...)

--
Danny Colyer (remove safety to reply) ( http://www.juggler.net/danny ) Recumbent cycle page:
http://www.speedy5.freeserve.co.uk/recumbents/ "He who dares not offend cannot be honest." -
Thomas Paine