Chaps

I have aquired an AST electronic speedo with no instructions..
On the back it has four terminals arranged thus:-

+ -

L G


Now '+' and ' - ' are you would think straightforward and the L is defintootly the backlight.

I have with it a transducer see pikkie which has only two wires on it. a black one and a white one. I've tried every combo I can think of but I can't make the beggar work. I strapped four magnets onto a sanding disk to simulate the prop
Any ideas as to how this might be wired or does anyone know please ?

Your thoughts, ideas, ridicule all gratefully recieved

Cheers


J.J

[Edited on 19/2/04 by jonti]
Rescued attachment transducer.JPG

The screen will almost certainly be ground / earth connection.

Have you tried asking the mfr?

Are you sure its the right sender - it looks like a typical industrial sensor to me. - any markings or ID on it?

lots of those sensors are not magnetic, and sense a metal object by capacitance, or the presence of a moving metal gear or some such.

if there is a screen, with a wire in it and a further wire, id guess screen = earth, screened wire = signal, other wire = power.


dont blame me if it blows up tho.....check all else before taking a risk


atb

steve

another take is

L = lights

g = ground

+ = power

- ?%#^^$??? could be signal?


atb

steve

Thanks chaps for suggestions

Both wires are just wires, neither screened

I'd already checked the continuity and theres nothing to the body and about 400ohms across the two wires, as Syd says, indicating bog standard transducer of some sort either field or capacitance sensitive.

I've no reason to doubt its the right sender, though it may not be I suppose. I suspect the guy who sold it to me (cheap I hasten to add) probably couldn't make it work either. Though if he sees this I'd gladly stand corrected.

Tried both metal flags and magnets

My first pass was power the gauge via + and - then one or other wire on the transducer to G then the other to ground. As I say I've tried a few different combinations since then and nothing even makes the needle twitch. I really need the definitive wiring diagram I suppose but the manufacturer was not helpful

I've probably already knackered it by now anyway...

ho hum...wheres that beer ?

if its a simple inductive transducer, you wont get much of a signal out of it unless it sees rapidly moving metal.

you really need some source of generating pulses that you could connect to speedo to see it it reads...

atb

steve

As I said in my first post, I used magnets stuck to a sanding disk and, prior to that, a metal flag in the chuck of a power drill.
I suspect my propshaft and/or anything else wouldn't rotate faster than that...

It may be buggered of course but unless I'm sure it's wired correctly I'll probably never know......if no-one comes up with a definitive wiring diagram I'll probably bin it......lifes too short.

Thanks anyway

Anybody got any other thoughts.......other than bin it

nope - i meant ditch the sensor, and get some means of giving pulses to the rev counter to see if that works. You would need to use a frequency generator / oscillator or similar

If it does work, you should be able to pick up some kinda sensor from farnell or rs components to replace the one that might be dodgy.

quote:

---

Originally posted by stephen_gusterson
nope - i meant ditch the sensor, and get some means of giving pulses to the rev counter to see if that works. You would need to use a frequency generator / oscillator or similar

If it does work, you should be able to pick up some kinda sensor from farnell or rs components to replace the one that might be dodgy.

---

same pick up as ive got,if i remember corectly one is a live from the speedo head and the other goes to earth

quote:

---

Originally posted by theconrodkid
same pick up as ive got,if i remember corectly one is a live from the speedo head and the other goes to earth

---

ive got some magnetic strip from a fridge door attached to a cv joint,just play around with the numbers till you get it right

Ok cheers
I'll have another play tomorrow

how can effectively wiring the two wires across the battery (as one will be gounded and one will be at guage 12v) work?

if anything, id say oen si earthed and the other goes to a signal pin, or power and a signal pin. but across power and ground - nah.

Or have I misunderstood?

atb

steve

steve,its the OUTPUT wire on speedo head,not ign live,that gives it the signal,and yes you are missunderstood

Not sure if this helps but ive got a VDO electric sender with the same type of pick up,on back of speedo the plug has 8 pins and i'm using 4 of them.

They are numbered so its as follows.

3/ = earth
4/ = ign live
7/ = sender
8/ = sender

My senders wires are the same colour and it didnt seem to make any difference which slot they went in,its obviously a feed and return and pulses at sender.

For Mr Gustos peace of mind...

One wire does parallel off the Live and the other does indeed go to "ground"? ... not chassis but the G tag on the clock probably doesn't mean "ground" but "gen" for sign gen or something

Seems to work anyway

Thanks again

[Edited on 22/2/04 by jonti]