alan Posted April 18, 2009 Report Share Posted April 18, 2009 in advance of Scotland i have just fitted a bicycle digital speedo, having heard that the ignition plays havoc with the wireless types, i fitted a wired one. all works well if freewheeling with a dead engine, but once the engine is running the speedo displays random numbers.. i guess the PVL coil is causing the problem... any one have a solution???? Quote Link to comment Share on other sites More sharing options...
wayne_weedon Posted April 18, 2009 Report Share Posted April 18, 2009 Are you using a resistor plug or cap? That may help. Another option may be to wind the sensor wire through a ferrite ring a few times. They can be found in dead PC Power Supplies or maybe at a Maplin electronics store. Wayne... Quote Link to comment Share on other sites More sharing options...
pete_scorpa3 Posted April 18, 2009 Report Share Posted April 18, 2009 I had that problem with a wireless one. With the bike on a work stand it worked perfectly, start the engine and it acted more like a rev counter. Quote Link to comment Share on other sites More sharing options...
mavric Posted April 19, 2009 Report Share Posted April 19, 2009 Mmmmm! Have a look at what they did in the 60's, that would be a starting point! I don't think that points interfered with the speedo cable too much? Clearly its not just the trick frames and carbs (which we all get so uptight about) going on Cheat fork internals, hubs, PVL ignition etc Will there be a bike that truly represents what was rode in the 60's at the start of the event never mind the finish. I very much doubt that the winning machine will truly (even nearly) represent what was actually rode in the '60s. Quote Link to comment Share on other sites More sharing options...
alan Posted April 19, 2009 Author Report Share Posted April 19, 2009 hi mavric, is that a picture of your cub on your profile page... looks quite trick to me................ I have steel petrol and oil tanks, original hubs, yokes, stantions and sliders, frame and swinging arm... i agree a cable operated speedo would be good, but i am only trying to make my bike a bit more road legal for scotland and the Northern bike rounds,.... Quote Link to comment Share on other sites More sharing options...
alan Posted April 19, 2009 Author Report Share Posted April 19, 2009 (edited) Are you using a resistor plug or cap? That may help. Another option may be to wind the sensor wire through a ferrite ring a few times. They can be found in dead PC Power Supplies or maybe at a Maplin electronics store. Wayne... thanks wayne I'll give that a go..... if not i will just have to rely on the fact that valves start to bounce at around 35 mph.. I was more concerned about the mileage.. It's tricky to work out MPG and therefore if and when to refill on road trials.. I usually only put in 3 or 4 pints for a venue trial and have the tap on reserve all the time. Edited April 19, 2009 by alan Quote Link to comment Share on other sites More sharing options...
wayne_weedon Posted April 19, 2009 Report Share Posted April 19, 2009 (edited) Alan Your problem is almost certainly RF noise coming from your ignition. The signal levels in the bicycle speedo are low and the RF is swamping the signals from the wheel sensor and probably being picked up in the cable from sensor to readout. As they are two separate circuits you also have a floating ground in the speedo, so another option to try and may be the simplest is to somehow ensure the Battery Negative in the speedo is bonded to your frame assuming you are Negative Earth, which using PVL? I would of thought so. This will either work, Not work or rare chance it fries the speedo depending on how well it's designed. Wayne... Edited April 19, 2009 by wayne_weedon Quote Link to comment Share on other sites More sharing options...
slapshot 3 Posted April 19, 2009 Report Share Posted April 19, 2009 AlanYour problem is almost certainly RF noise coming from your ignition. The signal levels in the bicycle speedo are low and the RF is swamping the signals from the wheel sensor and probably being picked up in the cable from sensor to readout. As they are two separate circuits you also have a floating ground in the speedo, so another option to try and may be the simplest is to somehow ensure the Battery Negative in the speedo is bonded to your frame assuming you are Negative Earth, which using PVL? I would of thought so. This will either work, Not work or rare chance it fries the speedo depending on how well it's designed. Wayne... thinking aftermarket accessories here Wayne........ Quote Link to comment Share on other sites More sharing options...
wayne_weedon Posted April 19, 2009 Report Share Posted April 19, 2009 thinking aftermarket accessories here Wayne........ Nah, but I did a few years ago make alloy bodies for these speedos to be used on road bikes There was a weird chain of events leading up to that work, all because a lost German biker got chatting to me at traffic lights while I was riding my Morini 500. But I digress... A lot of RFI issues can be reduced with good earth bonding techniques, I see issues like these on my cnc machines when bonding issues rarely arise. Wayne... Quote Link to comment Share on other sites More sharing options...
alan Posted April 19, 2009 Author Report Share Posted April 19, 2009 thanks wayne The fix seems to be to use the ferric ring ( Quote Link to comment Share on other sites More sharing options...
wayne_weedon Posted April 19, 2009 Report Share Posted April 19, 2009 Thats good Alan. Is it stable now? How much effect did the Ferrite have? Did Maplins have one? or did you get it elsewhere? One would ASSume that if the other device you talked about is designed for motorcycle use then they have designed it with at least some RFI precautions. Wayne... Quote Link to comment Share on other sites More sharing options...
alan Posted April 19, 2009 Author Report Share Posted April 19, 2009 Hi Wayne It will only work at all with the ferrite, and only then if mounted far enough away. I "borrowed"a clip on type ferrite from the video, I'll pick up a replacement from Maplins in leeds this week some time I wonder if there is a market for "fiddle" speedo ? Sensor pick up mounted in a dummy drive box, the wires fed through an RF sheilded dummy cable, to a D shaped housing to accept an off the shelf speedo head, Should be able to get Miller to knock em out for Quote Link to comment Share on other sites More sharing options...
wayne_weedon Posted April 19, 2009 Report Share Posted April 19, 2009 Fiddle Speedo Hilarious! You get him to and I'll make em for half the price eh and bring Jeff Bungay back just to sell them. Wayne.... Quote Link to comment Share on other sites More sharing options...
alan Posted April 19, 2009 Author Report Share Posted April 19, 2009 Fiddle Speedo Hilarious! You get him to and I'll make em for half the price eh and bring Jeff Bungay back just to sell them.Wayne.... not sure who jeff bungay is... but i'll photoshop an advert up... this time next year wayne we will be millionaires.. Quote Link to comment Share on other sites More sharing options...
wayne_weedon Posted April 19, 2009 Report Share Posted April 19, 2009 Should a fiddle speedo be accurate or waver all over the place to be authentic Maybe you should take that ferrite back out after all! Wayne... Quote Link to comment Share on other sites More sharing options...
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