ST162 digital dash, electronic speed sender - freq multiplier circuit?

**The Witzl** · 30-01-2007, 10:45 AM

Ok, this one's pissing me off....

putting an ST16x digital dash into an ST162 which is converted to 3S-GTE with an MR2 g'box with the electronic speedo sender.

The digital dash has a speedo cable input, which is then hooked to a optical interrupt pulse generator, creating a 24-pulse/rev speed signal into the digital dash.

The speed sender in the gbox is a 4-pulse per revolution sender.

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So, i need a 6x frequency multiplying circuit that can handle a pretty wide frequency range.

I've found the following circuit using an atmel AT90S1200-12, but im a bit newbie with Atmel shite and dont really want to go down that path.
http://www.edn.com/contents/images/52799di.pdf

The jaycar digital speedo corrector can only adjust +/- 100%, not enough.

Anyone got any ideas? It's really doing my head in, and i sooo dont have time to try and work this out during work hours (i'm beyond busy at work!)

Thanks.

**AndyTTR** · 30-01-2007, 10:09 PM

Can't you put the original ST162 mechanical sender into the new gearbox? If they're S53/54 boxes then it should be a straight swap? IIRC the speed sender isn't different for the digital dash.

If the car has the E series MR2 box in it then the mechanical sender from an AE95 4AGZE gearbox (not sure of the code) will slot in. Couldn't say if the speedo will read accurately though.

**cambelt** · 31-01-2007, 01:20 AM

VDO make a multiplyer box with 4 dipswitches on the front , about $90
Dave

**sideshow** · 31-01-2007, 07:30 AM

i have a unit that can do up to 3 or 4 times

but if i modify it u can get 5 or around 8

only prob is when your goin slow the speedo wll jump round

cause the more u multiply it the harder it is to get any device to be smooth at low rpm pulses

my units are way more complex than the jaycar shit

**The Witzl** · 31-01-2007, 01:49 PM

getting a mechanical speedo drive for an E-series box is not a pretty concept - they are fkn rare.

Dave, thanks for the VDO option

Sideshow - price me, and give vaigue internal components... ie, what chips used. (if i buy i would rip it apart with curiosity anyway). You know what im like, and i would prefer to learn rather than just buy the solution and forget it.

I might also look at other ways around this.... but that will come later

**CrUZida** · 31-01-2007, 04:36 PM

UZS131 Crown speedo senders are 20pulse/rev units.

**The Witzl** · 31-01-2007, 04:45 PM

hmmm... i wonder if that would fit.... i'll try to reef out the sender in the box and post a pic tonight.

**sideshow** · 31-01-2007, 07:42 PM

i have 3 2nd hand crown speedo drives

the circuitry for these units would be too big for u to make i recon

they are 150 plus gst

i think they have 2 circuitboards in them and 4 long chips

its nothing like what you get at jaycar

they are complicated but very accurate thats y i wont go near half assed components cause if its something i make and needs to be important it cannot break down caus i have to give warranty

if it was for a shitbox id build somehting worth 4 bucks

but for a 4 dollar part failing i cant waste half a days work travelling to fix the fuk up

if you goto my website theres a pic of the unit with the lid off in the products section

**brett_celicacoupe** · 31-01-2007, 08:04 PM

sounds like a job for logic.

im sure with my basic&dodgey atmel skills i could develop some code to make it work.

the accuracy of the other units would depend on how they spread the 6 pulses between the null in the 4 pulse output. logic would be up to job as you could refer to the last 4pulse event to gauge the spacing of the 6 pulses.

one other suggestion would be to modify the 24 slot disk to 4 slot. but i got no idea how feasable that is

**AndyTTR** · 31-01-2007, 08:26 PM

So the car has an E series box in it? It still sounds like you're doing it the hard way. I know a wrecker down here in Victoria that probably has the mechanical sender to suit the E box, i'm pretty sure it'd be less than $150 too.

**The Witzl** · 01-02-2007, 10:14 AM

Originally Posted by AndyTTR

So the car has an E series box in it? It still sounds like you're doing it the hard way. I know a wrecker down here in Victoria that probably has the mechanical sender to suit the E box, i'm pretty sure it'd be less than $150 too.

Andy - give me details please. That would be the best solution.
I'm pretty damn sure its an E-series box from an MR2.

Sideshow - thanks for the info. Yeah sounds like you have some programmable logic circuits, which is basically what i wanted to know, thanks

Stop bagging Jaycar, our kits are for hobbyists - not commercial grade!

Brett - visit the link in my first post, its got an ATMEL based frequency multiplier circuit on there, with the assembly code included. I've just never actually done my own atmel circuit before! If I can find someone to program the Atmel for us and give me a hand, i dont mind making the circuit just for kicks

Also checked the instrument cluster last night. Where the speedo cable would go in, it coverts the rotation to a 20-pulse/rev electronic signal. So it's only a 5x multiplier that I need.

**brett_celicacoupe** · 01-02-2007, 10:45 AM

talk to wilbo about atmel stuff.

what i know is what he showed me

from 31 Hz to greater than 30 kHz.

31 cycles per second is pretty fast, 7-8 rotations of the speedo cable per second. im estimating thats like 40k/hr at least.

edit; the simplicity of the project is such that you wouldnt bother with their code. unless you know how it works and understand it, it will be a headache to troubleshoot and modify.

Originally Posted by brett_celicacoupe

one other suggestion would be to modify the 24 slot disk to 4 slot. but i got no idea how feasable that is

try this?

**The Witzl** · 01-02-2007, 12:04 PM

Brett,

modifying the wheel isnt an option - the 20-tooth wheel is driven by the speedo cable, which doesnt exist in this car because it has an electronic speedo drive (which is 4-p/rev)