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 4digit 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.|
|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.
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