Here's a geeks take on it...

Here's a geeks take on it...
Posted By: FiveOh (38.220.252.2)	Posted on Date: June 24, 1999 at 08:46:12
In Reply to: UPDATE on Variable Shift Light.... JAY95gt on June 23, 1999 at 20:20:45:
Message Text:
Where did you get your 3000RPM resistance from? I ignored it and did a little math on it and found that the formula to calculate the necessary R for any RPM becomes: (RPM-1355.33)0.985=R This give the following R's 5203,5396,5589 & 5802 If you assume the pills are slightly off and then assume the 200ohm/200RPM, your formula becomes: (RPM-1410)1.0=R Your number will be right on. If this is true, your RPM pill errors are as follows: 5000=5000 5200=5200 5400=5390 5600=5580 5800=5790 I think I would average the error out and use the formula: (RPM-1418)1.0=R To give you: 5000=5008 5200=5208 5400=5398 5600=5588 5800=5798 In electrical terms, put 1418ohm resistance in series with your pot or the switch idea with each one having 200ohms. Good Luck, FiveOh : Well, the Autometer people are apparently smarter (or are they?) than the MSD people. Read farther down my board at my idea of using either a potentiometer or better yeeet, a series of resistors in series with on off switches to allow me to easily select any rpm value without buying a whole bunch of little pills. MSD uses a simple formula (add 1000 to resistance value to get rpm) such that 4000 Ohms is 5000 rpm, 2700 Ohms is 3700 rpm, etc. : I tested my Autometer pills and this is what I found: : RPM......kilo-Ohms (difference from rpm prior) : 3000.....1.88 : 5000.....3.59 : 5200.....3.79 (200 Ohms) : 5400.....3.98 (190 Ohms) : 5600.....4.17 (190 Ohms) : 5800.....4.38 (210 Ohms) : So, it appears there is approximately 200 Ohms/200 rpm OR 1 Ohm per 1 rpm, BUT, the scale doesn't fit for teh 3000-5000 spacing. That ends up being more like 170 Ohms per 200 rpm. : Do you think these are just production tolerance variances and that I may even be MORE accurate by starting at 3600 Ohms for 5000 rpm and go up 100 ohms for every 100 rpm? : Can someone else test their rpm pills and see what they end up as? Another rpm range would be great as well. : Thanks all - this idea wil be neat if I can get it all figured out.. : jay : 95gt

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Comments: : Where did you get your 3000RPM resistance from? I ignored it and did a little math on it and found that the formula to calculate the necessary R for any RPM becomes: : (RPM-1355.33)0.985=R : This give the following R's : 5203,5396,5589 & 5802 : If you assume the pills are slightly off and then assume the 200ohm/200RPM, your formula becomes: : (RPM-1410)1.0=R : Your number will be right on. If this is true, your RPM pill errors are as follows: : 5000=5000 : 5200=5200 : 5400=5390 : 5600=5580 : 5800=5790 : I think I would average the error out and use the formula: : (RPM-1418)1.0=R : To give you: : 5000=5008 : 5200=5208 : 5400=5398 : 5600=5588 : 5800=5798 : In electrical terms, put 1418ohm resistance in series with your pot or the switch idea with each one having 200ohms. : Good Luck, : FiveOh : : Well, the Autometer people are apparently smarter (or are they?) than the MSD people. Read farther down my board at my idea of using either a potentiometer or better yeeet, a series of resistors in series with on off switches to allow me to easily select any rpm value without buying a whole bunch of little pills. MSD uses a simple formula (add 1000 to resistance value to get rpm) such that 4000 Ohms is 5000 rpm, 2700 Ohms is 3700 rpm, etc. : : I tested my Autometer pills and this is what I found: : : RPM......kilo-Ohms (difference from rpm prior) : : 3000.....1.88 : : 5000.....3.59 : : 5200.....3.79 (200 Ohms) : : 5400.....3.98 (190 Ohms) : : 5600.....4.17 (190 Ohms) : : 5800.....4.38 (210 Ohms) : : So, it appears there is approximately 200 Ohms/200 rpm OR 1 Ohm per 1 rpm, BUT, the scale doesn't fit for teh 3000-5000 spacing. That ends up being more like 170 Ohms per 200 rpm. : : Do you think these are just production tolerance variances and that I may even be MORE accurate by starting at 3600 Ohms for 5000 rpm and go up 100 ohms for every 100 rpm? : : Can someone else test their rpm pills and see what they end up as? Another rpm range would be great as well. : : Thanks all - this idea wil be neat if I can get it all figured out.. : : jay : : 95gt :