micro-displ.jpg (31183 bytes)
Typical readout style (Cabin temperature)
micro-1.jpg (26746 bytes)
My development board with display showing "Low battery voltage"
click to enlarge pics.

Under construction!

GM T700/R4 lockup circuit, gear indicator and Hotrod monitor module.  April 23, 2000

My everyday job is in Electronics, so I have decided to put some of that, into my 1930 Ford Hotrod. I could have built a set of digital instruments, for example, but since I want my Rod to be more ‘resto’ style, analogue style instruments will be retained. In this case, VDO Cockpit Royale™ style.

As I also need a ‘gear indicator’ for my GM T700/R4 auto transmission and a speed sensitive lockup, I decided to make these functions electronic, and build it myself. As I thought about it, a few more functions could easily be incorporated by using  a small  4–digit LED display driven by a micro-processor.  Just a few examples are:- radiator electric fan control, warnings of low oil, battery voltage and brake fluid, etc The display will possibly be mounted under the speedo, in a new, enlarged, instrument panel.

Also, Lokar and other similar Hotrod shifters have no built in gear select indicator and an add on 'box' must be fitted to fit a small display in the dashboard, or elsewhere. I will incorporate this function also.

speed sensitive lockup of T700 auto trans
gear indicator for auto
control of the radiator electric fan
display of:- indicator direction, battery, temperature, oil and fuel 
alarms for low oil, fuel, water, battery etc
cabin temperature function
simple calibration procedure 

Since I'm familiar with some of the Motorola (tm) micro processors, I decided to stick with them, but use a new device, the M68HC908GP32 (tm).  For those not familiar with micro processors, this device is about the size of a small coin and is a complete self contained mini computer with it's own memory which must be programmed, in order to do anything useful. That's where I come in.  I will program it to do the above functions and more if I think of them.

For non-electronic minded Rodders and others, you can 'switch off' here. I'm going to talk a bit about the micro processor device itself.

The M68HC908GP32 device I have chosen to use is a fairly new member of the '68HC08' family and features 32kb of Flash memory and 512 bytes of RAM.  It has dual timers, SPI, SCI and an 8 input analog to digital convertor.

I plan to use the analog to digital convertor for monitoring various levels etc in the Rod and some of the other features will be used also. The micro also has a built in monitor program area which allows external simulation, control and programming of the flash memory.

For more information on the micro device:-

For more information on the device, see the Motorola 68HC08 web site
Free software, see the P&E Micro site
For a test board, with a micro mounted on it, see Mario Becrofts site.  
 gp32bd.JPG (32938 bytes) Mario's test board.  This board is about 3" x 1" and the micro processor is the square black device a little left of centre.

More information to come.

October 2003, Updated
August 16, 2010
See my 1930 Ford coupe  Hotrod under construction
  No guarantees are given or implied as to the suitability of this material for any purpose whatsoever.
68HC908GP32 Electronics and the Hotrod (1930 Ford coupe)
Here is a summary of what I hope to achieve:-


© . Percy 1999-20003