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tachograph speed pulses (simulator)

Anyone on here service/calibrate tachographs? or have knowlage of them???

I am building a bus simulator cab, and am working on the dashboard,

I have an arduino board that communicates with the bus sim program, and i have the outputs to work gauges and a rev counter that i used as a speedo, basically i have a square wave output that varies according to the speed (if i were to connect a speaker, i'd get a rising and falling tone as the speed goes up and down... anyone who knows arduino's, it is the tone generator function i'm using.

This worked the rev counter nicely, as it's basically pulsing to earth so many time a minute to get the needle to show the apropriate speed.

But now i have got a proper tachograph and things are a little different it seems.

The tacho is a VDO Kienzle 1318.27, 12 volt version.

I have the power and earth to it no problems, the speed input i have been trying to get working on the B plug, terminals 1 and 2 are +ve and -ve, and 3 and 4 are pulse inputs, according to the little diagram on the top of the unit, it seems to want a positive pulse on one wire, whilst getting a negative pulse on the other, is this correct?? it shows on the diagram a '2159' pulse generator used on those connections.

i assume that is the 4 imp/m signal,

There is also pin 7 on the B plug, and pin 3 on the D plug that are labeled V -imp, it seems that means speed impulse? is that an input or an output, the 4 imp/4 signal is referenced as a distance signal,

what i'm wondering, is there a way to feed the tacho a simple varying pulse to get it to work? or do i need to somehow convert my pulse output from the arduino, into a 'double pulse inverted' signal that the 2159 generator gives?

Reply to
Gazz
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You might find some useful information in

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is the full service manual for the 1318 also

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Reply to
Peter Parry

The 2159 impulse generator produces two signals. B1 and B2 provide the power to the generator. B3 and B4 are the speed signal inputs. The speedo of the tacho should work with just one but the tacho will pulse when stationery, 0-30 kph every 8 secs, as part of regulation diagnostics. The second signal prevents that happening. If you only have a single speed signal then apply it to the tacho pin 3. Take a second line from the same signal source and connect to the base terminal of a MPS A13 transistor. Connect the transistor emitter to pin B2 and collector to pin B4. Job done.

Pins B7 and D3 are speed output signals.

Reply to
kitaspyb

Excelent, thanks for that,

yup, i've got the needle swing to 30 and back every half minute, which i figured is due to it expecting an earthed speed signal on either B3 or B4 when stationary,

With a single speed signal, the needle waves around wildly upto 5kmh, at about 4.3kmh the needle will go full scale, and at 5 it will come back, then will read properly, is that part of the 'dodgy speed signal detected' electronics? or do i have another issue possibly,

The program that reads the simulators speed and puts out the speed pulses reads 0 to 1250 pulses, (the bus simulator is written very realisticaly, the speedo in the simulation/game gets it's reading from the rotation of the virtual prop shaft... so altering the rear axle ratio or tyre size in the code throws the speedo out, just like in real life)

But i have set the tacho's dip switches to all off, and am feeding it 10 pulses per kmh (the 0 to 1250 pulses, 0 being stationary, 1250 being 125 kmh... tho the buses in the simulator max out at 76kmh.. 1989 era german buses with voith 3 speed boxes)

Anyway, i'll go and have a play with a transistor and see if it works,

Reply to
Gazz

Hmmmm,

Just tried the tranistor jobbie, i didnt have a MPS A13 in my parts bin, but used a BC337, and it seems to work.... with B4 connected as desribed, the needle doubles the speed shown, which i have read is proving the tacho is getting the double pulses, however i still have the needle wobble below

5kmh,

Wonder if this could be a fault in the tacho, i have had the drive motor's cover off, and cleaned the resistive track under the output cog (drive motor unit operates as a servo i guess) the resistance changes smoothly as i move the cog when it's back in place,

So i'm wondering if it's a circuit board fault, afaik the signal i'm feeding it is smooth, as the speedo i drove before didnt show the needle wobble at all,

Reply to
Gazz

Hi The full scale travel will occur when the tacho is de-powered then re-powered and receives a speed signal, hence it will FSD at that low speed. The low speed fluctuation is caused by the low pulses being fed to the tacho. The lowest calibration settings of the DIL switches, is over 2000 pulses per km. Try setting the switches to 2 3 and 9 on with all others off and see if that makes a difference. If you can get up to

2400 pulses per km setting the switches 1 4 6 7 9 & 10 on will give you 60kmph at 2400 ppkm

Let me know how you get on.

Reply to
kitaspyb

Not got on well :(

it seems that anytime i set switch 8, 9 or 10 to on, the needle drive jumps to about midway, even with a zero speed input signal, so i can't seem to get it to accept a higher pulse count yet, will have another play tommorow, but wondering if something is screwed in the tacho for it to act like it does with the top 3 dip switches set to on,

Reply to
Gazz

Thanks for all the help to try and get this thing working,

Unfortunately i've given up and cheated, as the old speedo unit worked perfectly on the sim, i've given the tacho head a transplant, basically i've gutted the head leaving just the backlight bulbs and warning led's pcb's in place, then mounted the guts of the speedo on the back of the tachograph face.

obviousely means i've lost the milometer function and the clock, BUT i don't get the needle swinging to 30kmh every 30 seconds when the sim isnt running, or the needle wobble and FSD upto 5kmh all the time,

When mounted in the dash, it looks like a proper tachograph, the speed indicator needle moves properly and smoothly... and silently, i found the tacho's servo motor needle drive a bit noisy.

Reply to
Gazz

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