I forgot to mention that to get around the slow sampling rate for the tachometer. That is how do you measure a 1HZ signal faster than once a second. The trick I used was to count the time between edges. Thus I would count the time between rising edge and falling edge of the signal. This would allow me to sample 1Hz signal at 2Hz. Thus if you have a 2Hz signal you get 4Hz update. I eventually stop the speed of update to about 15 times a second as that it is fast enough.
Most inexperienced people with embedded design would count the number of pulses over a second which means that they can not tell the difference between a 2 Hz signal and a 2.5Hz signal. I found that for tachometers this give slow update and very poor resolution. This is why I use the other method. In the Pulsar 50 I implement the technique using the microcontroller. In the Pulsar 200 for the 15 inputs I use an FPGA to count the time between edges. The FPGA has far superior resolution that the microcontroller and thus is much more accurate. Trampas -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Trampas Sent: Tuesday, May 01, 2007 8:04 AM To: 'Mercedes Discussion List' Subject: Re: [MBZ] AVR based RPM meter for cars Here is a link to my website: www.sterntech.com I have a Pulsar 50 engine monitor I was building, it currently uses a PIC processor, if anyone wants one I can provide all the schematics and source code as well. I also have the Pulsar 200 which monitors just about anything you want, 16 thermocouple inputs, 15 inputs which can measure voltage, resistance, or frequency. Then it has two tachometer inputs and an inductive pick up. I designed these for experimental aircraft and have a few flying but at last the market is not big enough to make money from them thus I now have a real day job. The OBDII device was designed because a friend of mine needed a quick way to see if car was ready for inspection. Again I am not a marketing expert so I figured the world would want an open source OBDII scanner, boy was I wrong. Trampas -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Rich Thomas Sent: Monday, April 30, 2007 3:27 PM To: mercedes Discussion List Subject: [MBZ] AVR based RPM meter for cars This might be something some of you want to do. --R http://www.makezine.com/blog/archive/2007/04/avr_based_rpm_meter_for_c.html? CMP=OTC-0D6B48984890 _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
