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johnbullas · 03-28-2016, 08:03 AM

OK, an update

I now have an Arduino Mega and an LCD display with a shield (aka interface) for the Mega so the two can comfortably talk to each other

Reading around the subject it appears there are a wealth of cheap little stepdown devices to reduce the voltages behind the Mini 1275GT dash to the 3.3v or less the Mega can handle

The oil pressure, water temperature, oil temperature and oil pressure senders all tell the gauges what to display by increasing the voltage they can pass the the pressure or temperature increases, the variability of the reference voltage needed by the gauge means some are powered off of the voltage stabiliser (10v) other senders work with gauges using the system voltage (notionally 13.6v aka 12v).

In all these cases, the voltage passed by the sender unit will have to be mapped to enable the voltage at the Mega (via the stepdown) to be converted to a displayed value.

In the case of the tachometer (rpm) a 0/12v pulse exists for the Mega to monitor

In the case of the vacuum gauge a custom pressure/vacuum measurement device is required

In the case of speed the rotation of the speedometer cable needs to be monitored (and a turns per mile value used to convert to speed) else a hall effect transducer will need to be used in association with a magnet fastened to the rotating CV joint on the transmission (coupled to the road wheel) - alternatively chopper type detectors reliant on the passage of a chopper disc through the sensor might be viable but the chopper on a motorcar is typically part of the hub and the ABS braking.

I have produced a Flickr photo album of the items identified to date

Once I get something working I will update thing, I have the LCD displaying dummy outputs so making good progress!

03-28-2016, 08:03 AM	#7 (permalink)
johnbullas EcoModding Lurker Join Date: Mar 2016 Location: southampton UK Posts: 5 Thanks: 0 Thanked 2 Times in 2 Posts	progress (2016/03/28) OK, an update I now have an Arduino Mega and an LCD display with a shield (aka interface) for the Mega so the two can comfortably talk to each other Reading around the subject it appears there are a wealth of cheap little stepdown devices to reduce the voltages behind the Mini 1275GT dash to the 3.3v or less the Mega can handle The oil pressure, water temperature, oil temperature and oil pressure senders all tell the gauges what to display by increasing the voltage they can pass the the pressure or temperature increases, the variability of the reference voltage needed by the gauge means some are powered off of the voltage stabiliser (10v) other senders work with gauges using the system voltage (notionally 13.6v aka 12v). In all these cases, the voltage passed by the sender unit will have to be mapped to enable the voltage at the Mega (via the stepdown) to be converted to a displayed value. In the case of the tachometer (rpm) a 0/12v pulse exists for the Mega to monitor In the case of the vacuum gauge a custom pressure/vacuum measurement device is required In the case of speed the rotation of the speedometer cable needs to be monitored (and a turns per mile value used to convert to speed) else a hall effect transducer will need to be used in association with a magnet fastened to the rotating CV joint on the transmission (coupled to the road wheel) - alternatively chopper type detectors reliant on the passage of a chopper disc through the sensor might be viable but the chopper on a motorcar is typically part of the hub and the ABS braking. I have produced a Flickr photo album of the items identified to date Once I get something working I will update thing, I have the LCD displaying dummy outputs so making good progress!