Completely digital cluster! *Update "3" 9/8/07*

[archiebold]

As a second year student in a Electronic Engineering course, I was thinking about trying to create a completely digital cluster using seven segment displays for the speedo, tach, and trip odometer (keeping the regular odometer the old anolog to keep it legal) and have bar leds for gas, oil, and temp gauges using several op-amps as analog comparators. For the speedo and trip odometer i will be using a magnet countersunk into the cable itself where it attaches to the cluster and a magnet-switch to count the RPM's of the cable itself and decoding that into the displays, and using the wires going into the coil decoded to the tach. What do you guys think? Any suggestions for the electrical or actual design are welcome.
RJV

Update on 2nd page.
9/7/07 on 3rd Page
Update "3" still on 3rd page... Added 3 more pics!

[69shelby]

Speedo is not reqired by any law in the U.S.

[muscle_Car1]

:shock: Aren't you supposed to know how fast you are going?

They (COPS) yelled at me when my cable broke.

[69shelby]

No, there is no law, check it out.

[htchbck]

well heck, I was going to try to be the first to do an all digital custom cluster, but it sounds like you are much more qualified than me, since I'm just a car-builder/house-builder. Sounds awesome! I like the idea of a countersunk magnet... same principle as the old digital speedo I had on my mountain bike. If you can wire up the circuits to decode everything right then it shouldn't be too terribly hard to do. When I was brainstorming on this idea I thought about using a an LM3915 or some similar IC and some leds arranged in a semicircle layout to mimic an actual tachometer. Since the chip only has pinouts for 10 leds though, it would be kinda stupid unless you could figure out if it was possible to string two or more of the chips together (like you can do with decade counters and stuff) but if you could then you could get 20 or 30 leds and make it worth it... Then you could have different color LEDs for the optimum shift range and redline and stuff like that. It would take some tweaking, but you could get the LM3915 to read the signals the computer is already sending to the tach wires (since those signals just increase and decrease in voltage according to engine speed anyway) and then it would light the leds in sequence around the circle based on the voltages going to the tach... if that makes any sense... like I said, I mostly build houses and cars, and not circuits and besides, your idea of using 7-segment displays would probably look cooler than a circular array of LEDs anyway

[htchbck]

and no, there isn't a law about having to have a speedo... but you are still responsible for how fast you are going, regardless of whether or not you know how fast you are going :roll:

[archiebold]

Speedo is not reqired by any law in the U.S.

Sorry, I mispoke, I meant it is probably illegal to mess with the Odometer, hence me keeping the old one the same.

Then you could have different color LEDs for the optimum shift range and redline and stuff like that. It would take some tweaking, but you could get the LM3915 to read the signals the computer is already sending to the tach wires

I was thinking for the shift points having a couple binary comparators, one comparing the current RPM's to the set limit, while the other is slightly below the set, this way you have the below set showing a yellow when it is reached then shortly after, the one on the actual set limit showing red.

Is the lm3915 an op amp? Im pretty sure it is.
I actually have to go back to work now.. breaks over :evil:

Check out these leds for the segments... I was thinking about a 2 inch tall number: http://img214.imageshack.us/img214/1997/bivarmc4.jpg
mmmmmm.... blue :twisted: [/img]

[muscle_Car1]

Changing the Odometer isn't illegal. Turning it back on the other hand is.
I've swapped them out many time. You just cant claim it as actual mileage.

[5.0zone]

Speedometer ! I don't need no stinken' speedometer.

Mine actually quit for a few weeks and I would just know how fast I was going. My daughters didn't know how. But that's what happens when you drive a car for 468,000 miles, that's right it tripped today on the way home from work. only 32,000 more to go :lol:

Top 10 ways you can calculate your speed in a Festiva.
1) Just wet your finger and stick it out the window
2) You know that your tires start shaking when you get over 55, 60 or 65mph or all three.
3) You can tell your speed by the pitch of wind going over your car or by the whine of the fan belt.
4) The out of round right rear tire syncs up with the out of balance left front at 72mph and you feel like a bowl of jello.
5) You know what your car/engine sounds like at 35,45,55,65,70,75,80,85, pegged.
6) You know how fast you are going by how far you have the volume turned up on the radio.
7) You have to roll up the window at 45 so you can hear the person on your cell phone.
8.) You know you are close to 70 in 3rd gear when it does not accelerate anymore and the pedal is to the metal :lol:
.
.
ok that all I could come up with, someone help me out with the next 3.

[packrat427]

8.) You know you are close to 70 in 3rd gear when it does not accelerate anymore and the pedal is to the metal

[htchbck]

9.) Whenever you are going over 75 on the freeway the doorframe will start flapping.

[pole120]

6) You know how fast you are going by how far you have the volume turned up on the radio.

My favorite

[nautical_lifens]

you hit a puddle at 65 and it sounds like a bomb went off.

[htchbck]

Is the lm3915 an op amp? Im pretty sure it is.

Nah, its just a logarithmic bar driver... but i'm sure you could use an op-amp too, I was just already familiar with the LM3915... its the driver that is commonly used on the audio VU meters, where it lights a 10 segment led bar graph depending on input voltage, in that case audio signal, for a tach, it would be the tach signal coming from the ECU.

I just thought of something else last night. You could probably very easily convert the fuel and temp to use the bar graphs and LM3915 since the fuel and temp guage use varying voltage to control the needles. That way besides maybe a few resistors and diodes all you would need for each of those would be a chip and 10 segment bar graph.

[muscle_Car1]

5) You know what your car/engine sounds like at 35,45,55,65,70,75,80,85, pegged.

I actually could do that in my old festiva