DMC optical sensor warning!

L

Laverda6

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Scottish Borders
My series 2 Jota has been of the road for 5 weeks. The crank sensor on the Moto Witt ignition failed.
The part is made by Honeywell and is no longer made. I tried in the UK, but no luck. Tried Italy no luck.
At long last Moto Witt had found one old stock. The problem occurs that sending a parcel to the UK
is a no go area for small companys as there is so much paperwork involved. Eventually it was sent
from a private address in Germany. So anybody with a DMC/2 be warned.
 
I've no problem with my 1912 Humber, maybe Laverda made too complicated motorcycles?
Some even had electronic ignition, the ones with points will outlast them by far.
Paul
 
Industry standard slotted opto HA21 from memory, many sources sell them, have many here you can have for postage if that helps, Not critical the specifications, post something here later today for reference, though really you will have to treat these plastic optical lens as consumables. Served a purpose now more reliable robust hall effect are the choice many a time. HTH j

p.s. not sure, however i suspect Paul M has a favorable position on points, just a suspicion that comes across the odd time.

Universal type that may work? Not seen a DMC optical stator plate, to my uncertain recall.... this one can be had from Farnell world wide wholesalers, RS components also i would suspect, refurbishing the original pcb should be possible


Only 11,000+ in stock at Digikey....

1696018855897.png

or this for DMC vertical slotted shutter

1696019165950.png
 
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Insomnia curing post, Some background on crank encoders or sensor basic design philosophy, DMC uses sensor turned ON for trigger signal ie the shutter has a cut out in a circular device, this has a preconditional element of being of electrical noise vulnerability. DMC could use high side switching to mitigate the low noise immunity, never bothered to research.

My background is industrial and commercial electronics and electrical areas, never been a low cost domestic bent. When you hold all switches ( sensors ) on then noise immunity is more certain, and can be fail safe mode also, sensor goes open and fault is obvious at that moment. IIS opto had one shutter to open a sensor for correct signal point, made testing each opto possible as there is not full circle skirt of the shutter to deal with ie DMC.

Hall Effect was different as it could handle the opto isolator led current on the iis module pcb direct and as such had very high noise immunity in that any unwantted stray electrical signal had to supply 10ma or more of current to mis trigger an opto isolator, never happen, used opto isolation on the input signal and output drives of the microprocessor, proved to be good design and never had a mircoprocessor fail from spurios voltages. j
 
John,

The manufactures say they will last forever but in actually they do have a limited life span. Usually the LED burns out. A number of companies here in the US made electronic ignition conversion kits to get rid of the points using an opto sensor on older cars. They burn out the LED after about 10 years of use. Almost always when you are hundred of miles from home and it is getting dark.

As for the DMC using high or low side switching, I would bet they use low side as it is cheaper to implement. Also faster (may not matter for an ignition) as the parasitic capacitance of the photo transistor is grounded so it will charge a little faster.

Bruce
 
As Bruce points out, the practical application of optics in harsh environments, has many facets. Main issue i looked closely at was contamination of the plastic focusing lens, by heat and oil, residual compounds of the heated oil. Boiled the slotted opto's in heated oil and tested the transfer ratio, given it was the most easy to test for in a hot bath ( and cold ice bath ).

Led current was crucial in the transfer ratio, when parameter tolerances, device to device was tested, pulling the photo transistor out of saturation when using low led currents to mitigate device self heating ie the led can slowly cook itself with excessive led current to ensure device to device parameter deviation is allowed for, still allowing a fully saturated photo transistor. Yes i know why did you start reading this, a grin here, j
 
Tah.... basic spec sheet, enough to work out a suitable substitute, not sure why am bothering, false sense of useful effort, and just because i can and Bruce also well able to spec a substitute have little doubt. Does the DMC have fly wires on the plastic housing ie not pigtails as usual... yes its a term in electronics "pigtails" why lie when reality is stranger that fiction...j
 
Haggis said:
This is lurking in my PC - double check the specification before use.
Haggis said:
Do it John, you are better qualified than just about anyone to find us Witt users a safety net substitute. :)
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Thanks for that, Haggis. Never know, might come in useful one day ...

And yes please John, if you can work out a replacement for the Honeywell original, I for one would be most grateful.
 
1200ts said:
Does anyone know what part number is marked on the ignition sensor used by Moto Witt. Other than it was made by Honeywell, I dont know what they used.
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I have a 750 kit waiting to be installed and its sensor says "Mexico 9214 HOA1881-12" confirming Haggis' reference and so we should be safe with the OPB880T55Z that Digikey claims is a direct substitute.
 
arancia said:
I have a 750 kit waiting to be installed and its sensor says "Mexico 9214 HOA1881-12" confirming Haggis' reference and so we should be safe with the OPB880T55Z that Digikey claims is a direct substitute.
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I'm in US and will be travelling to UK second half October, happy to order a batch and deliver to anyone in UK that would like to be the distributor there, if of interest let me know asap please, US unit price is $5.39 plus tax and local shipping.
 
Had a look at the TTE spec sheet for the suggested substitute device, lacks rise and fall time spec, not clear the transfer ratio, mechanical dimensions could be compatible though can be addressed at fitment stage, if nominally different.

As demands allow will see what Vishay has in the product range. HTH j.
 
Haggis said:
Do it John, you are better qualified than just about anyone to find us Witt users a safety net substitute. :)

I wonder if the subs suggested here hit the spot...
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The Omron at initial inspection has the electrical specifications i would think compatible with DMC, Farnell option above. Well done Haggis, the Omron is very expensive and in not for new design status, ie 350 available and that is the end.

Would be looking at the $2-4 price bracket and in quantity pricing ie 50 or 100 piece part purchase. There appears to be saving grace for you lot of slotted opto tragics.... die hard tragic flat earthers, a smile here. j

p.s.
just had a look across the product range from my usual suppliers, leaded ( fly wire ) slotted optos are in the $7+ price range, no getting around that, Vishay included. Should the Omron meet mechanical matching to the Obsolete Honeywell then you may have a part to use.
 
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