Jump to content
Electronics-Lab.com Community

Digital Dash - help please

Recommended Posts

I want to replace the current working dial gauges with digital read outs and or led bar graphs, using the current wiring harnesses for the inputs.  Here's what I want in the dash..nothing special. I got all of the tech. information out of a service manual for my car

Speedometer - 3 7 seg displays and 20 LEDs for a graph (1 at every 5 M/H, the car can't go over 100M/H ... darn rev limiters) Selectable M/H or Km/H would be nice as I go to Canada sometimes, but M/H is more important as I live in the US
--60 M/h at 1076 RPMs of Vehicle Speed Sensor, 60Km/H at 637 RPMs of Vehicle Speed Sensor

Tachometer - 2 7 seg displays and 8 LEDs for a graph (1 at every 1000 RPMs, the car redlines around 8000 RPMs)
--100 RPMs at 200pulses/min. of Ignition Control Module

Odometer - 6 7 seg displays, I want it setable to start from what the car has now

Trip meter - 3 7 seg displays, resetable counter

Fuel Gauge - leds or displays(Fuel Tank capacity is 11.9 gal) not picky
--resistance from float is 105-108ohms Empty and 3.5-5ohms Full

Temp. Gauge - leds or displays, not picky
--thermistor ranges from 20Kohms to 0.1Kohms

A/T position Indicator - P, R, N, 4, 3, 2, 1 it's a Honda, so it has a D4 and D3.  I know how to display each one on it's own 7 or 13 seg display, but I wanted to be able to display them all on a single 13 seg

I want to do all of this using ICs and discreet components to keep cost down. I have schooling in Electronics, so wiring and soldering are not problems for me
Link to comment
Share on other sites

  • 1 month later...

It's not going to be simple.

You need a way to convert the analog signals (voltages) to digital. You can use a series of comparators to drive each LED as the thresholds get tripped. This is kind of a brute force approach, but isn't complicated.

A better solution might be to use a microcontroller with an internal A/D convertor and then use an output port to drive some transistors to actually supply the power to the LED's.

Link to comment
Share on other sites

I admire your idea but what you are asking for is not an easy task.

Truthfully, if you surf the web concerning the vehicle you own in reference to digital auto guages the package may already be available as a plug-in.

People get the impression that building a kit or designing/constructing a project will provide a savings concerning cost.
Sadly, the latter is generally incorrect, a small simple circuit will allow a savings but a large project will usually cost more.

The other dilemma you encounter with your project is the environment, extreme cold (winter) and/or extreme hot (summer) place a toll on a project not designed for the purpose.
Cheap, inexpensive parts concerning the above will only create a lot of frustration down the road. 

Link to comment
Share on other sites


You are very correct. There is no simple circuit for something like this. The cheapest approach is to use something already made and modify it to work. Properly constructed the environment isn't really a big problem. Most of this stuff would not be very sensitive and even with a uP design temp is not a big problem.

However, as Omni said it may be a MUCH better idea to use something that is already proven. 1984 Corvettes used an all LCD dash. Not LED's like you asked for, but it is an all digital dash. I'm sure there are others and I know for a fact that the aftermarket makes LCD dashes.

In the end it's your choice how to go. There are some IC's that are voltage meter IC's. They drive LED's directly so that a yet another method of doing it yourself.

I just recently found this forum and I'm glad I did. Lots of people willing to help and because we are from all over the world you get to see many different approaches. What could be better?

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...