View Full Version : Digital Gauges

11-10-2006, 01:06 AM
What would matter to you. the accuracy or the refresh rate of a digital speedo or a digital RPM?

I can refresh the display faster, leading into more faster readings, but the accuracy then decreases. Or I can get accurate results, but at 1 second refresh rates versus like 300ms.

11-10-2006, 11:50 AM
Dood, that refresh rate would annoy me! I think I could stand to be off 1 mph. Would it get more accurate as acceleration decreases?

11-12-2006, 05:08 AM
It would be the same. If the refresh rate was set to 450ms and you were driving 30mph, the reading would be 28-32mph (-/+ 2mph). The faster the refresh rate, the bigger the gap. The default is around 900ms and that provides a accurate reading.

11-12-2006, 05:32 AM
Don't care about the speedo... care about the tach.

11-12-2006, 05:36 AM
Don't care about the speedo... care about the tach.

I thought you were some kind of super driver? Who looks at the tach?

11-12-2006, 06:23 AM
I've worked on the tach portion a little bit... 200ms refresh rate, about -/+ 20 RPM. I think I will put this little project aside for now. It can read the speedo, RPM, and voltages. I should probably work out the kinks to that stuff before I start on fuel level, and all the other stuff.

11-12-2006, 08:18 AM
Well the tach (if I were to use one in a future project) is important when it comes to selecting gear ratios to dictate how well the car is staying in the powerband around the corners on any particular track. I'm really interested to see how this turns out. I've always like the Motec gauges which are... digianalog? That's the best way I can think of putting it. Where it climbs across a dial like an analog gauge but gives you readouts of where the shift points were.

11-12-2006, 04:52 PM
Hi Acidice333,
I was thinking of attempting to read the signals for RPM and Speedo for a small Microcontroller PIC project I was about to embark on...
I have a JDM ST185 Gen5, and I need to know the type of signals that are output from the motor. Done some looking around, but can't find a lot of info on it. Mine has an electronic sender for the Speedo, not cable, and I need to know the type of signal it sends. Now I don't have a oscillocscope, so I can't check the type of signal...
Do you know what signal it spits out, square or sine wave?
Also same goes for RPM, haven't found much on this, again I need to know what type of signal it sends to the clocks...
If perhaps you know (or anybody else please) what type of sensor is used to send the info to the clocks, is it one pulse per rotation of shaft, or several if it's some type of slot/led sender, that would be most useful?
I could just experement, and I probably will actually, one of my reasons for this was to adjust my Speedo from 120MPH, up to a less embarassing (:)) 160/180. I know these modules can be bought, but if I succesfully do this, I could make an adjustable module that can be set by the the installer to a GPS system. This would also be handy if anyone changes tyres to different diameter, just keeps speedo spot-on accurate.
Having recently got back into PIC chip programming, I thought of what I could do in my car... Some sort of small display on dash, possibly a mobile phone type display that shows things like battery condition, A/F ratio, RPM, Speed, Engine Diagnostics, Knock sensor etc... Possibilities are endless, info would be most usefull for tuners, or just tinkerers like myself...
Any info would be most helpfull.