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D Reg 18S Revcounter 12V ?


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im trying to get my nodiz ignition unit to power the manta rev counter .

the nodiz outputs 5v so ive got some diodes to make it work like this ....see pic below

but , what happens is this , idle speed is working at about 1000 as i rev up to 2100 its fine, above that it falls to zero until it drops below 2100 again .

I did assume the standard rev counter uses a 12v feed ?

and i did get the bloodly things the wrong way round the first time , could that have damaged the diodes and be why its playing up now ?

any ideas welcome :-)


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It's years since I did electronics, if I remember correctly the most basic diodes are like one way systems with the current flowing towards the line so in your diagram it's going nowhere

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I'm no electronics expert so no guarantees with this,the bottom diode is a Zenor diode that will only conduct in the direction it is connected in your circuit at 15 volts,so may be when you rev the car the volts drop and it stops conducting so i would try a lower voltage Zenor diode i think.

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i had a go at it again , i bought some different zener diodes from maplins . a 12 and a 16 volt .

the 12 made it drop out at a lower revs about 1700 .

the 16 got me up to 2300

so i put them in series along with the 15 and got 2500ish....

its heading in the right direction so i think i need a much bigger diode ... like a 50 or something or just keep adding more lol

ive tried doing some research but its really beyond me .... there's some kind of avalanche point after which the zener diode will allow current to flow in the opposite direction


its been fun messing about but i think ill leave it to the experts at nodiz to sort it out before i start a fire .

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