jans@mako.UUCP (Jan Steinman) (09/27/84)
[The opinions expressed by my parents made me what I am today.] I just received my new Cateye Solar (latest Bike Nashbar unadvertised special price: $49.20 + s&h) and it's better than I had imagined. However, it has the same problem that most other cyclometers (including mechanicals) have: you can't start the odometer at an arbitrary point. I tie my bicycle PM to the odometer -- I have on my old Multito the number of miles (less a few dozen due to broken belts, etc.) on my Holdsworth, and have logged the mile at which I last trued the wheels, replaced the chain, etc. and I wanted some way to continue doing so. A DVM told me that the wheel sensor was a simple magnetic reed switch which had to sink about three volts from the cyclometer, so I hooked up a reed relay to the output of a signal generator with disappointing, erratic results. The signal generator could not source enough current to drive the relay reliably. A consistant, much better solution was to use a transistor. First, set your cyclometer wheel diameter to "2999". This setup will saturate the interrupt bandwidth of the cyclometer, so you want to rack up the miles as rapidly as possible -- you can't simply up the signal generator frequency to get a MPH you like. Be sure to use a square wave source of about one volt positive. Unless you plan to do this often, hold everything together with clip leads or use a solderless proto-board. Any garden-variety PNP transistor will work. The cyclometer contact nearest the "set" button is the positive current source. I used a time-base generator set to 50Hz which gave me 86MPH and put 1000 miles on overnight. Any resistor that will keep from blowing the base-emitter junction (a few hundred to a few ten-thousand ohms) will work. DO NOT connect any signal source directly to the cyclometer! Doing so may damage the cyclometer and may void the warranty! Unless you use gobs of signal ( more than 8 or 10 volts) the transistor should isolate the generator. +-----------------------+ +---------------+ | Signal Generator | PNP C | Cateye Solar | | (square wave) | +--+ | (underside) | | (aprox 0 to +1V) | B | / | | | | | ______|/ | | | | | 1-47k | |\ | | +-----+ | | + O-------------/\/\/---+ | v E | | SET >-+ +-< | | | | | | O | | | | | | - O-----------------------------+ | | | | | | | +-----------------------+ | | +-----+ | | +---+ | +-----------+ | +-----------------+ (You shure wake up tired after putting on 1000 miles overnight!) Have fun! -- :::::: Jan Steinman Box 1000, MS 61-161 (w)503/685-2843 :::::: :::::: tektronix!tekecs!jans Wilsonville, OR 97070 (h)503/657-7703 ::::::