Speedo pulse converter

[celicapain]

Howdy happy toymodders
Ive got one of those speco electronic speedometers running off an mx83 speedo sender and ive got an issues with the fact that the mx83 speedo sender doesn't send out enough pulses per KM for the speedo to read( from memory sender output 2400 pulses per K, minimum val accepted is 3000 (stupid f****n design))
Anyone know where i could sort a device to double my pulses to get my speedo happening-i really wanna know how fast im going now that im nearly getting it finished.

thanking you very muchly optimistically and in advance

[CrUZida]

Get a Jaycar one.

[o_man_ra23]

You need a phase lock loop which increases your frequency. This is most likely what the Jaycar kit Cruzida mentioned is.

[wilbo666]

You need a phase lock loop which increases your frequency. This is most likely what the Jaycar kit Cruzida mentioned is.

That interesting use of the term "Phase Lock Loop" ...

http://en.wikipedia.org/wiki/Phase-locked_loop


You don't really care about the phase in this case (IMHO), i.e. a Frequency to Voltage converter and then a Voltage to Frequency converter (with the right ratio) would work, and doesn't care about the phase at all!

Including phase would just make it unnecessarily messy for no reason as I see it (in this case)...

The Jaycar kit uses a PIC if I recall...

Sure "Phase Locked Loop" is a nice term to throw about, but we aren't trying to make an accurate local oscillator here...

Cheers
Wilbo

[o_man_ra23]

Depends how accurate you want your speedo to be I guess. Voltage drift is always fun.

If you double the pulse output, a PLL will work perfectly, and just like the mechanical gearing setting an accurate pulse, your PLL will output an accurate pulse. This helps if your electronic speedo has ODO.

[wilbo666]

Depends how accurate you want your speedo to be I guess. Voltage drift is always fun.

If you double the pulse output, a PLL will work perfectly, and just like the mechanical gearing setting an accurate pulse, your PLL will output an accurate pulse. This helps if your electronic speedo has ODO.

I wouldn't use a F->V and V->F myself, I was just trying to show that the use of a PLL in this case was overkill

If you were going with just doubling it tho as opposed to adjusting it then I can understand And looking at the manual for the gauge, and seeing that it is adj, your PLL would work fine


Anyway looking at the problem I think there might be something else wrong?

I think MX83 has a 637 Speedo Cable Revolution / km dash (On the non-grande models...)

The gears in the Grande gearbox are the same if I recall, so the digital sender on the Grande MX83 is 637rev / km.

The digital speedo sender on the MX83 is 20 pulse / rev if I recall. So that goes to 637 * 20 = 12740pulses / km...

This is well within the 3000->30000pulse / km that the speco gauge accepts?

Have you tested your speed sender?

Cheers
Wilbo

[o_man_ra23]

Depends your diff ratio and wheel size. What car is this on?? The RA23?? If so, you need to look at the number of teeth on the gearbox's drive gear, the number of teeth on the MX83 sender, the ratio of the diff and the diameter of the wheels. Then you will be able to work out your pulse/km accurately. It may be within your specs, but if it is out, simply doubling with a PLL will be the easiest solution. Anything else is more complex than it needs to be.

[wilbo666]

The digital speedo sender on the MX83 is 20 pulse / rev if I recall. So that goes to 637 * 20 = 12740pulses / km...

This is well within the 3000->30000pulse / km that the speco gauge accepts?

Have you tested your speed sender?

Cheers
Wilbo

Either his diff and tyre combo makes ~12740 get to less than 3000, or greater than 30000 (his diff and tyre ratio needs to make it either ~ -73% or ~ +135% to put it outside what the speco gauge can adjust for... Or other very large / silly / impossible to get numbers as a result of tyre and diff changes lol)

The other options that I can see are

1) He doesn't have a MX83 speedo sender, he has something that is 4 pulse / rev

2) His speedo sender isn't working...


From the sound of it his speedo might not be working at all...

...to get my speedo happening...

Even with the speco gauge set at 3000 and with a 4 pulse per rev sender it should be working, just on the low side...


Anyway, looking forward to seeing what he says

Gauge Datasheet:
http://www.speco.com.au/Downloads/sp...tionmanual.pdf



Cheers
Wilbo

[CrUZida]

4 pulse per rev is the standard that aftermarket guages are tuned to.
20 pulse per rev is something Toyota did for a very short time (MX83 and UZS131 are the only cars I know that used it).

[wilbo666]

GZ20 and MZ1x are 20 pulse / rev too that I know of

Looks like the speco gauge needs that tho, 4 pulse falls short....

Cheers
Wilbo

[celicapain]

soz, I should have been clearer, with my problem- The speedo is working perfectly, with my current setting of 5400 pulses it reads exactly half the speed im actually doing e.g at 100km/hr speedo says 50km/hr.
I calculated the pulse setting i needed based on tyre size, diff ratio and g/box output and im pretty sure that its correct for my car, especially as when i double the speedo reads accurately(well 50%)

so in summary
assuming wilbo's speedo rev thingo is correct, remembering that the mx83 is 4 pulse per output
637 x 4 = 2547 pulses per k, just under the 3000 pulse minimum

so either frequency to voltage- then voltage to frequency
or
gz20 or mz1x series speedo sender.
methinks im gonna have to go see the toyotoa wreckers again!

thanking you all for your advice,
have a tops day!

p.s rep must be spread around grumble..

[CrUZida]

If all you need to do is double the pulses, go get a $45 JayCar speedo corrector kit.

[wilbo666]

I was told MX83 was 20pulse / rev!

I'll test one when I get home I thinks

Anyway in that case what Cruz has suggested will prbly be your easiest option

Link to it:
http://www.jaycar.com.au/productView...Max=&SUBCATID=



Cheers
Wilbo

[o_man_ra23]

Get a 20 pulse speedo drive... it will be easier and one less link in the chain.

[wilbo666]

Well, just tested a MX83 sender, and you are 100% correct they are 4 pulse / rev. Not 20pulse / rev as I had been told...

My apologies!

Finding a 20pulse / rev one may not be that easy :S

Cheers
Wilbo