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Speedo/Tacho - Converting electronic to Mechanical
jimgiblett - 20/1/10 at 12:20 PM

I thought I would try to dip into the font of knowledge that is Locostbuilders

I am looking for a box of tricks to convert an electronic pulse from a gearbox speed sensor and tacho to a mechanical drive for my old Alfa clocks.

Similar to this

http://www.hawksthirdgenparts.com/electronictomechanicalspeedometerbo x.aspx

There are a couple of companies in the US but they either don't respond to my email or are expensive.

Any help much appreciated.

Jim

r1_pete - 20/1/10 at 12:26 PM

Try Alan Davies at "The Gauge Shop", may be able to help out, or even convert your units.

blakep82 - 20/1/10 at 12:32 PM

how would that work? a box that takes an electronic signal, and the maybe spins a motor to drive a cable to the clocks? you'd then maybe need to get your clocks recalibrated if theres a converter box already availabe, or expensive to have one custom made from scratch

converting your clocks to run electronic might be easier i'd think. stepper motor to drive the needle, could then be reprogrammable and set to run in any car with electronic speedo output


edit: ah, should have clicked the link first its expensive

[Edited on 20/1/10 by blakep82]

jimgiblett - 20/1/10 at 12:38 PM

Hi Pete

Do you have contact details? I have googled and only found an ebay shop.

Thanks

Jim

jimgiblett - 20/1/10 at 12:44 PM

quote:
Originally posted by blakep82
how would that work? a box that takes an electronic signal, and the maybe spins a motor to drive a cable to the clocks? you'd then maybe need to get your clocks recalibrated if theres a converter box already availabe, or expensive to have one custom made from scratch

converting your clocks to run electronic might be easier i'd think. stepper motor to drive the needle, could then be reprogrammable and set to run in any car with electronic speedo output


I think that is exactly how they work, complicated and perhaps prone to failure. I just wanted to avoid butchering the clocks which are a quite rare but this may be the only solution.

- Jim

blakep82 - 20/1/10 at 01:12 PM

ah, that was going to be a question i was going to ask but forgot, the one about rarity etc. makes sense

r1_pete - 20/1/10 at 01:26 PM

I've U2U'd alan's email Jim.

jimgiblett - 20/1/10 at 01:48 PM

Thanks Pete

02GF74 - 20/1/10 at 02:22 PM

I looked into this very early on and built one after my first SVA failure.

My car was fitted with mechanical speedo that was not geared correctly for my car.

I use a PIC to drive dc motor - stepper motor could not be used due to the speed.

PIC = microcontroller, this would receive pulses and provide voltage - from memory, PWM - pulses of varying width to alter the motor speed.

It was going all fine and dandy untilsome cog in the speedo jammed and I abandonned that idea in favour of an after market electronic speedo.

Just before I spent my money., I did look into using a stepper motor to move a needle round hte speedo face but could not find a suitable LED for the odometer so abandonned that idea.

So yes, it can be done.