12v AC powered motorbike with DC Speedometer wiring

Thread Starter

joswat94

Joined Jun 30, 2017
5
Hi everybody,
This is my first time here and i'm hoping you can help me!
I don't have a lot of electrical knowledge so when my new speedometer showed up in the mail and had one less wire than the original i was stumped.
after a little research I realised that it ran on DC while the old one ran on AC. A little bit more research and i came across something called a full bridge rectifier which probably sounds a bit more familiar to you guys and girls out there but seems like it would fix the problem. If so I am still not sure about the specification of the rectifier needed or how many i would need or how to wire it up haha.
Please find the wiring diagrams of the bike and the speedo attached. sorry about the picture quality.
Cheers,
Joe

speedo wires.jpg
IMG_0722.JPG
 

Thread Starter

joswat94

Joined Jun 30, 2017
5
HI there,
cheers for the replies.
Dodgydave the back of the unit looks like thisIMG_0724.JPG
the big screw thing on the back connects to the front wheel which clocks the distance and speed (as far as i know) so the wires are just for the leds on the display of which there are 3 visible and one backlight as far as i can tell. so i think i'm going to be using the wires for bulbs of the high beam indicator, turn signal indicator, neutral indicator and speedometer light that are shown on the far left slightly above the middle on the diagram.
Strantor, that's good news right? so the whole circuit is already in DC?
sorry about my noob knowledge. let me know if there any info i'm leaving out that's essential.
Cheers again,
Joe
 

LesJones

Joined Jan 8, 2017
2,665
I think like the other members that replied I assumed that it was an electronic speedometer that was driven by pulses. I don't think you are right about AC and DC. Looking at the wiring diagram it looks like there is only one turn indicator light where your old one had two. Also the backlight on the diagram shows a 3W normal bulb for the speedometer backlight. On your diagram you show an LED backlight. If it is an LED backlight it may require a current limiting resistor in series with it. (The limiting resistor may be built in.)

Les.
 

Thread Starter

joswat94

Joined Jun 30, 2017
5
Ok great cheers again for the help guys. I have emailed the manufacture about the current limiting resistor for the leds.
Les you commented on the single indicator wire instead of the old two wires. Do you know how I would deal with this?

Thanks again,
Joe
 

GopherT

Joined Nov 23, 2012
8,012
@joswat94
Black from new Speedo to ........ Black on bike
Red from new Speedo to.............Green on bike (if you have on or more extra green wires, connect them to this group)

LightBlue from new Speedo to ........ SkyBlue on Bike (right Turn)
Orange from new Speedo to ........ Orange on Bike (left turn)

Black/Gray from new Speedo to ........ Brown on Bike (speedo back light).

Red/green from new Speedo to ........ RedGreen On bike (neutral indicator)

Dark Blue from new Speedo to ........ Blue on bike (high beam)
 

LesJones

Joined Jan 8, 2017
2,665
Hi Joe,
You should be able to connect the original left and right indicator wires to the new single indicator via two diodes 1N4004 or similar diodes would be suitable. The positive ends of the diodes (The end with the band.) would be connected together and to the new single indicator bulb. The negative of one diode would connect to the original left indicator wire the negative of the other diode would connect to the original right indicator wire. The mention of a LED backlight was in the wiring diagram in your first post . Does this refer to your original speedometer ?
What was the fault on the original unit ? (The speedometer part or one of the lights not working ?) I don't think the wiring diagram matches either the new or old speedometer unit as it only shows 4 bulbs but it has seven wires. If all of the bulbs were working on the old unit you shold be able to test if the backlight is a bulb or LED using a multimeter on the ohms range.If they are normal bulbs they will have a low resistance. (Less than 20 ohms.) If it is an LED it will probably seem to be open circuit as the test voltage would be too low to forward bias the LED junction.

Les.
 

Thread Starter

joswat94

Joined Jun 30, 2017
5
Ok great guys I have some diodes in the mail. Honestly Les I'm not sure what I was talking about with the led backlight haha. The main fault with the old speedo was its aesthetics honestly (although nothing on it was working). I almost feel confident I can do this now. One last question though, am I going to be able to connect the diodes to the wires with crimp connectors? It's what I was planning on doing it all with but I'm not sure if this is appropriate.

Cheers,
Joe
 

GopherT

Joined Nov 23, 2012
8,012
Hi Joe,
You should be able to connect the original left and right indicator wires to the new single indicator via two diodes 1N4004 or similar diodes would be suitable. The positive ends of the diodes (The end with the band.) would be connected together and to the new single indicator bulb. The negative of one diode would connect to the original left indicator wire the negative of the other diode would connect to the original right indicator wire. The mention of a LED backlight was in the wiring diagram in your first post . Does this refer to your original speedometer ?
What was the fault on the original unit ? (The speedometer part or one of the lights not working ?) I don't think the wiring diagram matches either the new or old speedometer unit as it only shows 4 bulbs but it has seven wires. If all of the bulbs were working on the old unit you shold be able to test if the backlight is a bulb or LED using a multimeter on the ohms range.If they are normal bulbs they will have a low resistance. (Less than 20 ohms.) If it is an LED it will probably seem to be open circuit as the test voltage would be too low to forward bias the LED junction.

Les.

The original single-lamp speedo had only one bulb for turn indicator, the NEW one has an arrow for each direction. The fewer number of wires on the new speedo is because there is not a ground wire for each bulb.

No diodes are needed. In the original, the left connects to right at the speedo to light the turn-signal indicator on the speedo (see schematic). One will be grounded and the other will be "on" to light the indicator.

On the new one, the "on". One to to the common ground to turn on the correct one of two indicator lights.
 

Thread Starter

joswat94

Joined Jun 30, 2017
5
Ok i'm just waiting on the crimp connectors to wire it up. Thanks again for all the advice everyone, I'll let you know when it is working.
Cheers,
Joe
 
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