Well, we have moved house after 19 years. I knew we had to do it, as to leave it any longer would mean we'd be too old to consider it, and we'd be just stuck in a place we had finished with. But the effort has been huge, and of course the BMW has been relegated to a very low priority, what with preparing the house for sale and then all the packing and, of course, the emptying out of the shed.
As I had written earlier, when the battery boxes were removed, I installed the larger fan. This required chopping into the existing cowling.
The new, bigger fan is 200mm in diameter and has a nominal maximum flow of 1220m^3/hr. It runs off 48V. A new, 48V 150W DC/DC converter has been installed in the boot under the rear parcel tray. Testing the fan with its sensor lead held at 5V (a full-on situation) resulted in current of 4.75A. (228W) Grounding the sensor lead switches it off.
It is being driven with a 2kHz PWM signal to the base of a NPN transistor whose collector, held at 5.1V with a zener diode, connects to the fan sensor lead. I've set up the PIC micro to read the voltage on a thermistor on the motor windings -- a thermistor additional to the one for the Wavesculptor -- and to set the mark/space ratio accordingly. The fan is set to come on at about 40deg and increase in 20% steps to be full on at 125deg. It's pretty loud at full whack.
Just to get the car going, I repaired the wiring from the encoder that had
fouled the fan, put everything back -- and still no go. So out came all the boxes again and I did what I should have done before: put the digital scope on the encoder outputs. One channel was dead, due probably to V+ shorting to the collector with the chewed wires. So out came the motor and a new encoder installed. Rather unnecessarily I also removed the clutch, and then realised I didn't need to dismantle the whole motor just to get the encoder in its end-plate off.
All was re-assembled and I then knew I had put the clutch disc back in the wrong way round -- some vibration in the transmission resulted although the car was able to be moved. The message was loud and clear: stop trying right now!The removalists were coming in a week and I just put the car in its existing state onto the car-carrier truck for transport down south.
Unfortunately, something happened on the way down here and the car wouldn't start to unload it from its truck. On looking into it, I saw that a pre-charge resistor was split, so no pre-charge and consequently the main contactor would not be allowed to close.
How did the carriers manage to achieve this fault? I had left clear written instructions on how to drive the car.
They must have managed to switch on the ignition with the accelerator depressed while simultaneously somehow putting it into gear. I'm amazed at the unconscious creativity of others in generating faults in one's equipment. And the lesson, I suppose, is to work harder to make things foolproof.
In fact, some time ago I achieved a similar result, shattering a pre-charge resistor, by driving the WS from the computer config. software whilst forgetting to close the main contactor. The high current draw requested by the WS was sufficient to destroy the resistors.
I can draw a couple of conclusions: firstly, the button-style bi-metal cut-outs beneath the resistors are ineffective in preventing failure as they are much too slow to respond to high current episodes.
Secondly, I need to prevent the WS from drawing current until the main contactor is closed. I can arrange this by taking a signal from the contactor control circuit
(the collector of the transistor in this circuit) and passing it to Pin 7 of the DCU, this pin being the brake signal input. When this pin goes high, the DCU disallows WS current draw.
The house we are currently renting, while very pleasant, unfortunately lacks a sizeable shed. I have negotiated the use of a suitable shed nearby in which to work on the car.
The effort of moving house brought us down with illness and we are slowly recuperating. And very slowly getting back to dealing with the car. Last week I re-registered it, and drove it round to its new workplace.
To be continued -- slowly!
We may have an easy software solution for you and it may not require the faster velocity telemetry (except possibly to datalog the nature of the problem).