pickup voltage required

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adrianb
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Joined: 23 Mar 2016 13:11
Location: sydney, australia

pickup voltage required

Post by adrianb »

Hi,

Does anyone know the voltage required on the pickup lines to trigger a spark in the regular black 500 transducers. I've got a troublesome pickup that doesn't seem to be generating enough energy to consistently trigger a spark. I've tested the transducers are firing ok with an external signal. It's a bit tricky to accurately measure the voltage spike I'm getting on the pickup line but it doesn't seem to be more than about 0.5v

Cheers,

Adrian
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72degrees
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Joined: 31 Aug 2007 21:24
Location: West Midlands

Re: pickup voltage required

Post by 72degrees »

When I was thinking of rigging up a shift light system I did some prodding around with a multimeter:

"1500 mV AC (corrected!) direct from a red pickup connection but connecting the multimeter significantly slowed the idle, so hooking in to that doesn';t seem like a good strategy for best performance."

That was at idle speed though I'd guess significantly less at kick start speed so 0.5v doesn't sound too bad.

The only sure way IME to prove a faulty pickup is a substitution test.
adrianb
Posts: 10
Joined: 23 Mar 2016 13:11
Location: sydney, australia

Re: pickup voltage required

Post by adrianb »

Yes, well I've got an original red pickup and a NLM pickup both of which seem to struggle. In fact the NLM one has never worked properly. So I'm 'substituting' them for a Sachse unit :)
I'm curious to know what the actual figures should be though, i can trigger it no problem with a 1.5v battery but I don't have a variable power supply to get an accurate threshold trigger point. I presume it's the increased voltage from the pickup with rpms that effectively gives you the advance curve?
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72degrees
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Re: pickup voltage required

Post by 72degrees »

From my rusty O level German and looking at the graphs in this article I think there is more to it than just voltage. Voltage wave peaks per minute would be my guess but have a look:
http://www.motomoriniclub.nl/zuendung.pdf

It may be that you should get nearer 1.5v at kick start speed. My tests were aimed at rpm detection rather than poor function.

The Sachse unit seems to be the 'Rolls Royce' solution but I like a no-battery-needed system - particularly for racing. The Sachse set up needs conventional coils anyway and I've found a NLM module with XV250 or even 'scooter' coils works really well with an OEM red pickup. I gave up with an NLM one. I got it working but the performance boost didn't live up to promise and set up was extremely fiddly. The NLM module will work with any conventional analogue pickup apparently, so if necessary I can get a Nuvaray black type if my red one fails.

Are you sure your stator coil is up to snuff? There are three factors to a good original system (ignoring plus, caps and HT leads). IME if anyone of them is below par then it will never run as well as it can. With the Sachse, however, the stator ignition coil is redundant. Not the lighting coils though, so they better be in good nick and rotor magnetism strong or you are going to need a big battery.
adrianb
Posts: 10
Joined: 23 Mar 2016 13:11
Location: sydney, australia

Re: pickup voltage required

Post by adrianb »

Hi, from the document 1.38v +/- 10% seems to be the magic number, which fits in very nicely with what I observed on the bench.

Having seen the design and gained a bit of insight into how Ducati/Morini did things; a sort of elegant simplicity coupled with a 'good enough' attitude seem to be the design principal. All those A/C waves from stator and pickup increasing in strength and frequency together with a bit of high-school electronics work together in a sort of orchestrated dance to produce a not quite precise spark that's near enough to the optimum curve, so they called it a day and went to drink some wine. If they had been German they just wouldn't have quite been able to get to sleep.

I'm ok with the idea of having a battery, especially now that Lithium ones make even the weight seem pretty insignificant. I can use the juice from the ignition coil and feed it in as well. I was toying with the idea of having a 'battery assisted' regular ignition setup, which would make up for any aging of the ignition coil and/or aging of the leg on the kickstart. I don't think it would be that hard actually, but as my problem was with the pickup it wouldn't have helped me - and before anyone starts - no I don't mean just wiring the transducers directly to the battery ok.
Al B
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Joined: 03 Feb 2017 20:34
Location: Luton, UK

Re: pickup voltage required

Post by Al B »

This might help

viewtopic.php?f=4&t=4316

Though at the time of posting my result I had a mish-mash of ignition parts. A red pickup and grey transducers which are supposed not to work together but seemed to do so just fine. I've subsequently changed to the modern blue transducers but haven't re-tested the pickup output signal. Maybe a job for the weekend
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72degrees
Posts: 1549
Joined: 31 Aug 2007 21:24
Location: West Midlands

Re: pickup voltage required

Post by 72degrees »

Al B wrote:This might help

viewtopic.php?f=4&t=4316

Though at the time of posting my result I had a mish-mash of ignition parts. A red pickup and grey transducers which are supposed not to work together but seemed to do so just fine. I've subsequently changed to the modern blue transducers but haven't re-tested the pickup output signal. Maybe a job for the weekend
I once discovered which combination of red/black pickup and grey/black transducers worked on a hotel car park in France. IIRC red pickup with grey transducer did work, but as this was to revive just one cylinder it did seem a bit lumpy afterwards. I think it may have put the advance out on the 'mismatched' cylinder. Perhaps running two grey transducers it's not so noticeable or can be compensated for by adjustment?

I've also found that the cheap digital tachos work OK on four stroke singles (tested on the Gilera 175 up to 6000 rpm!) and also on a Morini twin (but only at idle rpm so far). Not so successful on a 2T single like the KTM I referred to in that thread if you don't choose the right setting ;)
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