Hello anyone who is willing to help, First of all happy...

Question by garry kemp
Submitted on 1/18/2004
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Hello anyone who is willing to help, First of all happy New Year! I have had this website suggested to me regarding the following inquiry and its worth a try. I drive a Peugeot 405 diesel and would like a digital speedometer for it as at present the needle "flutters" on mine. I have been all over the web for the past year or so trying to find help but have been unsuccessful. I have been faced with the following problems: 1) I have no real knowledge of the complexities of digital electronics 2) I have purchased a digital speedometer from jay cars in Australia for $64 but it only registers in kilometer's per hour (mph is not an option unless you have knowledge of PIC chips and know how to alter the code). It is based on up to six magnets secured to the drive shaft and a coil attached to an aluminum bracket to pick up magnetic pulses as the vehicles moves, the unit itself is self calibrating by pressing a button at say a speed of 100km/h (after the over speed alarm has been selected to equal 100km/h), the PIC chip then calculates the number of pulses picked up in that time space and obviously calculates accordingly for rotation/pulses slowing down or speeding up. Unfortunately when the vehicle is stood still and you accelerate the speedometer registers a value. I have no idea what this means, I have used the screened cable they supply but beside that, in the united kingdom the speed limits are set in miles per hour and not kilometer's. In my mind I would like one that would register on either two or three 0.5 inch seven segment displays (preferably incrementally/decrement-ally), the circuit would obviously consist of a display driver to do this (maybe similar to a frequency counter), a multiplexer is mentioned in some similar circuits/articles that I have read, but I don’t know anything about them, a clock consisting of crystal for the purpose of creating the update time to change data, a debounce switch I have read for the purpose of cleaning signals/pulses and then a counter circuit to count pulses from the magnet and coil. Have anyone ever designed/built one of these if so how much for one or the design of it? I would like a working speedometer hopefully with more accuracy than the fluttering needle thing! I am a genuine beginner, I have only a very basic knowledge of counter circuits in the form of decade counters, I don’t even understand up/down counters. Can anyone please can you help me? Yours faithfully Garry Kemp United Kingdom

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Answer by Ryan Cunningham
Submitted on 10/18/2004
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I am currently working on a speedometer circuit. The prototype will have about 60+ blue LEDs around the guage like a normal speedometer that will stay on all the time. On the inside and outside of this will be rows or red LEDs offset a little for appearance. The red LEDs light up incrementally to indicate speed. If your interested in this email me at ryandcunningham@netscape.net and I'll discuss it with you. I'd appreciate it if you would say approx. how much you would be willing to pay if this product was available commercially.

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