When the normal power is applied the output of the 4N25 going to the MCU is basically a closed switch. If the resistor is open then the switch is also open. This just a basic schematic, additional component and values will depend on Battery voltage, resistor value capacitor,etc.I am not familiar with this semi conductor set up, could you run me through how this works?
Hello their... all of you you need a who's watching the Watchers. That is a real scientific term that I just made up.it would be necessary to test the resistor with a discharge current.
Just knowing that the resistor is present by passing a low test current etc.. is not good enough
This purpose does not make sense. A more detailed explanation pf what is intended to happen when that resistor is switched on may provide some understanding.It's a safety measure; the resistor discharges the circuit in an emergency, therefore ideally I want to be able to monitor it and make sure that in an emergency, the discharge relay will be opened and the discharge resistor will be able to discharge the circuit. It may not be possible, but I thought I would post it up here to see whether any of you guys (which almost definitely have more component knowledge) knew of a way of checking that it is still a working resistor.
There is nothing in any of those figures to indicate that the battery connection must be off for the discharge circuit to enable. Thus my comment. If the need is simply to assure that all capacitance in the inverter circuitry has discharged, the very simple scheme of multiple LED plus dropping resistors would both discharge and indicate the presence of charge in the circuit. And the cost for a quadruple redundant scheme will be far less than the switching device shown.Post #4 shows that the resistor is to discharge the inverter capacitance, not the battery.
Running the battery to flat dead is the poorest possible choice that there is! Disconnecting the battery is far more sensible, but that still possibly leaves the hazard of a charged capacitor inside the inverter package. Evidently that is the hazard that the TS is intending to reduce. It may be possible that in the event of a violent collision the vehicle may be damaged enough so that the inverter package is opened and the internal connections could be touched. It might also be that an individual not familiar with the internals of an automotive inverter system would open the package and contact a charged capacitor.It's an electric car. You might consider discharging the battery to "zero" and damaging it as a reasonable precaution before servicing the electronics; I don't. Usual procedure with any car is to disconnect the battery.
Congratulations, that's what the TS is trying to do and is the problem my comments tried to address. But then, your comment (below) indicates you needed the TS to clarify that the battery was disconnected despite clearly showing it that way and making common sense.Running the battery to flat dead is the poorest possible choice that there is! Disconnecting the battery is far more sensible, but that still possibly leaves the hazard of a charged capacitor inside the inverter package.
There is nothing in any of those figures to indicate that the battery connection must be off for the discharge circuit to enable.
What we see is that it is possible to disconnect the battery before engaging the discharge circuit, but there is nothing that demands it being disconnected.Congratulations, that's what the TS is trying to do and is the problem my comments tried to address. But then, your comment (below) indicates you needed the TS to clarify that the battery was disconnected despite clearly showing it that way and making common sense.
View attachment 214806
OK, and here is a generic answer: In many fire alarm systems there is a function called loop monitoring, where a smal current is constantly flowing through all the devices in the circuit being monitored. The supervisory system constantly observes that current and signals an alarm if it changes beyond some limits. You could monitor a small current flowing through that resistor and verify that it was within some limits, indicating that the main resistor was still in place.The TS said: "This is a generic schematic, with the resistor I need to monitor in red."
I asked the question about disconnecting the battery before activating the discharge circuit back in post #13.
To my understanding that was verified in post #19.
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by Luke James