Author Topic: Possible dynamo hub hook-up problem  (Read 543 times)

Possible dynamo hub hook-up problem
« on: September 25, 2020, 07:29:33 pm »
I am just mounting a dynamo hub and front light (for winter and possible touring purposes). The hub is a 3D-37 (Shimano) and the light is a Spanninga (entry level, can't remember the power but only 13€ and homologated in Germany and France). The light comes ready wired and there's no metal contact with the frame so no mass connection other than by wire. The dynamo is standard Shimano so using two wires into the lego block. No rear light, the most basic set up.

There is no indication on the light whether one wire is intended to go to hub mass (or on the card it came with). Yes I did look!

Spinning the wheel with all mounted on the bike the light is slower to light up than I expected and a lot less powerful. My only basis for comparison is the set up I built a couple of years ago for my daughter which was a C-3000 hub and a Union front light of a similar entry level to mine. That flashes bright the moment you move the wheel (her buddy says blindingly bright!). By comparison this one is quite anaemic and needs a good spin of the wheel to light up at all. I thought all the entry level Shimano hubs would be very similar as far as output was concerned!

The question is is there likely to be a sense to the wiring in the light? The outputs for a rear light I think have a sense with one terminal marked mass but there is no way to transfer that information to the wiring going into the light. The hub is a 3w hub marked 400-716 (which I take to be acceptable wheel diameters, mine is 650Bx38 so in the range).

Any ideas acepted. It's not a blinding mission stopping issue but it would be nice to know, especially if wiring backwards could kill the light.

Edit: the light is this one https://www.hubert-cycles.com/phare-classique-dynamo-pile/52479-projecteur-led-pour-dynamo-moyeu-spannin-8715117021696.html

Re: Possible dynamo hub hook-up problem
« Reply #1 on: September 25, 2020, 07:35:32 pm »
Go here, select the light, click downloads , check the PDF’s

https://spanninga.com/product-category/headlamps/?swoof=1&pa_power-source-type=dynamo-en&really_curr_tax=44-product_cat

They may or may not help

Kim

  • Timelord
Re: Possible dynamo hub hook-up problem
« Reply #2 on: September 25, 2020, 07:36:14 pm »
Wiring backwards won't kill the light (it's AC).  Worst case, it'll short the dynamo (which is also harmless) and it simply won't light up.  So that's probably worth a try, in case one side of it is getting not-very-well-earthed somewhere.

If the light has a standlight, it might not reach full brightness until the capacitor is charged?  In which case, try riding it.
Careful, Kim. Your sarcasm's showing...

Re: Possible dynamo hub hook-up problem
« Reply #3 on: September 25, 2020, 07:46:06 pm »
Thank you Phil and Kim. The PDF on the sceen is the same as what is on the card with the lamp but a lot clearer when on the sceen. It appears that they mean me to interpret the wire identification (white dashes on the insulation) as polarity indication - and I am the wrong way round! So tomorrow I will rewire the lego block and see what happens!

No there isn't a stand light on this one as far as I know. Not seen it mentioned and it would be unusual at that price point.

FifeingEejit

  • Not Small
Re: Possible dynamo hub hook-up problem
« Reply #4 on: September 25, 2020, 07:58:00 pm »
I find my shimano 3N-80 doesn't provide enough power to run my B&m IQX when wheeling the bike down the drive, both the SP-8V and SONDelux cause a flashing of the led at that pace.

What I do find however is the shimano provides more brightness at lower speed with 700x25 than those other 2, the SP is on a 26"x1.5 while the SON has 700x30

Would need to have a proper look at the output charts.

Sent from my BKL-L09 using Tapatalk


Re: Possible dynamo hub hook-up problem
« Reply #5 on: September 25, 2020, 08:07:55 pm »
simple suggestion; rather than rewire the plug, you could simply remove the lamp housing from the bracket (or the bracket from the bike) temporarily and see if the light becomes brighter when you do that. 

If it does, you need to rewire the plug.

If it doesn't you have an unrelated fault. For example one stray strand of wire in the plug can cause problems....

cheers

Re: Possible dynamo hub hook-up problem
« Reply #6 on: September 25, 2020, 09:11:46 pm »
I find my shimano 3N-80 doesn't provide enough power to run my B&m IQX when wheeling the bike down the drive, both the SP-8V and SONDelux cause a flashing of the led at that pace.

What I do find however is the shimano provides more brightness at lower speed with 700x25 than those other 2, the SP is on a 26"x1.5 while the SON has 700x30

Would need to have a proper look at the output charts.

Sent from my BKL-L09 using Tapatalk

LEDs differ too. I have a supermarket dynamo front light (no switch) which will light quite happily from a USB nomad battery which is only giving out 3.8v on test and a torch with the leds direct wired that needs 4.8v from 4 AAs to light. Both rated at 6v! The dynamo light would be quite usable as a front light with the nomad battery! (And yes I know they are not meant to be used with DC. The torch was my usual front light with a pack of 4 AAs, only problem was the fragility of the wiring to the battery pack)

simple suggestion; rather than rewire the plug, you could simply remove the lamp housing from the bracket (or the bracket from the bike) temporarily and see if the light becomes brighter when you do that. 

If it does, you need to rewire the plug.

If it doesn't you have an unrelated fault. For example one stray strand of wire in the plug can cause problems....

cheers

I don't think I would gain anything, there isn't any connection through the lamp casing, it's all plastic. I looked at that before wiring the lego block. If there is a stray wire, either it is in the lego block - in which case I'm going to fix it - or in the lamp, in which case since it is all sealed there is not much I can do that won't be destructive. Since I've already had to extend their wiring because it only just reaches the fork crown and I needed to go higher, I've probably already broken any warranty conditions!

Re: Possible dynamo hub hook-up problem
« Reply #7 on: September 25, 2020, 11:22:15 pm »
reversing the connections in the plug can only make a difference if

a) the plug is wired badly (near short or near open circuit) and/or

b) there is more than one earth return connection somewhere else in the arrangement.  If the lamp housing in plastic and you don't have a rear light attached (which might have a ground return connection in it, some still do), then it cannot possibly matter which way round the wires are connected to the plug.

In principle you are correct to be worried about ground return connections; not all shimano hub generators have a ground return but DH-3D37 does;



Models with no ground connection have a connector with a bigger offset to one side and no obvious ground connection (metal part extending from one connection to the locknut)

FWIW it is always a good idea to bench-test the setup  before starting to install it on the bike, make brackets, extend wiring etc.

NB one of the faults I have heard of (but not seen myself)  in relation to DH-3D37 is that the output windings can go  open circuit (or at least high resistance).  If you test the current output and it doesn't make at least 700mA into a dead short there may be a fault of this kind.

cheers

Re: Possible dynamo hub hook-up problem
« Reply #8 on: September 27, 2020, 01:37:28 pm »
I have rewired the lego block and now have a much more responsive (and apparently brighter - although having not tested at road speed that may have been an illusion) light.
The Spanninga however still appears less violent than the Union at the same price point (but the Union has a much deeper shape which fits less easily on my bike). But both give a nice flash the moment you move the wheel; it makes you look to see who else is flashing a torch in the garage, most surprising!
There may be something I have missed in the light fitting. Due to a lack of space in the garage I had to take the wheel out before unplugging the block and just a slight rotation of the hub gave a bigger flash than I expected at the light. I don't really see the point of a mass connection through the bracket when the light is already wired. Otherwise there is some other sorcery somewhere, switch or rear light connection, that I don't understand. They are very clear on the polarity of the rear light hook-up!
Anyway it works and seems bright enough for me. Finding a decent way of mounting it is going to be a lot more difficult (my present arrangement risks future problems with the barbag).

Re: Possible dynamo hub hook-up problem
« Reply #9 on: September 27, 2020, 03:12:31 pm »
with DH-3D37 and a ground return type rear light in use, you need to have everything connected correctly.

There is indeed 'no point' in a ground return connection (other than some redundancy I suppose) with most hub dynamos but ground return is still the usual arrangement for other types of generator, and I think that is why it persists in rear lights.  Many front lights share components with an unswitched model which uses a ground connection too, so you can understand why it persists in some models.

cheers