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68HC908GP32 Electronics and the Hotrod (1930 Ford coupe)

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.

Here is a summary of what I hope to achieve:-

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 

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

Under construction!

More information soon.

Any ideas ?  Email me

Glenn's Home Page Syntrx IC22S Hotrod Electronics

See 1930 Ford coupe  Hotrod under construction

Modified December 30, 2003                              (C) G. Percy 1999-2004

No guarantees are given or implied as to the suitability of this material for any purpose whatsoever.