DIY LED Tacho

**Mattzxr750** · 8th January 2009, 16:28

Originally Posted by gixxer-king

wel that was an anti climax. did it work or not, i want photos

So far no luck with getting it going it looks okay. But i think the schematic is wrong. Heres a cuple of pics for now.

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Originally Posted by motorbyclist

how much did all the bits cost?

All up about $40

Originally Posted by motorbyclist

and what, roughly, is the rev range covered? how adjustable is that?

it should cover most, it is adjusted by R3

**Mattzxr750** · 8th January 2009, 16:47

V2 has FAILED

...

however this brings me on to V3, a circuit of my own design. Using the manuals for the LM 2917 and LM3914 i have come up with one of my own to try and i think this one will work

**imdying** · 8th January 2009, 16:51

Keep posting!

**AllanB** · 8th January 2009, 17:03

Looks like a subway train map to me .......

A nice wee project there - post pics when finished please.

**motorbyclist** · 8th January 2009, 21:52

Originally Posted by Mattzxr750

it should cover most, it is adjusted by R3

damn, i suppose i should get my electrical hat on and have a look at that then - will be good revision before uni starts again

then i can have a tacho on my pocketrocket

**gixxer-king** · 9th January 2009, 10:37

perhaps posting up what is/not going and where you have tested the know it alls here could offer some input? many hands make light work but maybe many heads can make led work?

**motorbyclist** · 10th January 2009, 22:59

now call me a noob, but dont both the lm2917 and lm3914 require a +15V supply, not 8V as per specified in the OP diagram?

**craisin** · 15th January 2009, 07:38

this part-time know it all thinks it would be easier to mark maximum speed in gear on your speedo face

and save your money for your vices

**NordieBoy** · 15th January 2009, 08:30

Originally Posted by craisin

this part-time know it all thinks it would be easier to mark maximum speed in gear on your speedo face

and save your money for your vices

And if your vices are motorbikes and electronics?

**motorbyclist** · 15th January 2009, 11:01

maybe he doesn't have a speedo or tacho?

is there any more info on the required signal? my pocket rocket has two wires - the HT lead and the kill switch, and i think the only way to get a signal may be to wrap a few turns around the HT lead

**NordieBoy** · 15th January 2009, 16:17

Originally Posted by motorbyclist

is there any more info on the required signal? my pocket rocket has two wires - the HT lead and the kill switch, and i think the only way to get a signal may be to wrap a few turns around the HT lead

The trigger wire leading to the coil?

**motorbyclist** · 15th January 2009, 21:20

there is no trigger wire

just an HT lead and kill switch... i could use the kill switch but i think it'd kill the motor, chip, or both... same for the HT lead

it's one solid unit, which is a right pain in the ass cause you have to replace the whole thing if you lose spark - at a total cost of $8 for a new one

that's 5% of the total value of the bike! several tanks of gas! a third of a slick tyre!

**NordieBoy** · 16th January 2009, 07:19

My DR speedo said to either wrap 5-6 times around the HT lead or solder to the trigger wire.
I could never get a clean signal off the HT. Maybe something to do with the twinspark head.

**craisin** · 16th January 2009, 08:05

Originally Posted by motorbyclist

maybe he doesn't have a speedo or tacho?

is there any more info on the required signal? my pocket rocket has two wires - the HT lead and the kill switch, and i think the only way to get a signal may be to wrap a few turns around the HT lead

got a speedo. But the needle has been over-revved off the tach