Electrical Engineering


Making a simple IMA bypass connector from an old pack relay board

Making a simple IMA bypass connector from an old pack relay board
simple IMA bypass connector
The IMA battery can be completely removed from the car, and the car will still function, if the DC/Dc converter can have the HV input it requires.
The typical way to do this is to remove the whole connector/relay board from the pack, and use it to make those connections.
If the fuse and connector from a used pack is available, a much safer and simpler IMA bypass can be construced.
You remove the DC/DC connector, the 30A fuse, and make up some wires with ring terminals, and make a short bypass connector with those components. It is important to keep everything well insulated, and prevent ant possible shorts, so here is how I made mine.
If you can leave the HV battery in the car, just pull the "A" connector of the BCM and turn off the HV battery switch
location of BCM A connector

Making an isolated hall effect current sensor with ring terminals

Making an isolated hall effect current sensor with ring terminals
simple isolated current sensor
Needed an isolated current sensor to sense the current in my cell level test fixture. Found a neat part made by alegro that has a compensated hall effect sensor with built in current shunt. Unlike a regular current shunt where the resistance of the shunt produces a voltage when current flows through it, this device has an integrated hall effect circuit built in. The device comes in many flavors, with unipolar or bipolar sensing up to +-150A. The best part is that the hall circuit is electrically isolated from the current path. The down side was that the device was designed to mount on a PC board, so attaching it to the big 1/4" studs that I required was dificult. I carefully straightened the heavy copper buss bar leads and sawed a slot in some heavy 1/4" ring terminals. The terminals were soldered to the straightened leads, and the fine hall effect wires were connected to three wires and strain relieved with some hot glue.
Works like a charm.

Measuring resistance of less than 1 ohm

Measuring resistance of less than 1 ohm
measuring less than 1 ohm accurately
Having some issues with the resistance of a db-25 cable, and need to compare the end to end resistance of several brands to find the lowest resistance.
Unfortunately when using most DVM's, the sub ohm accuracy and resolution is pretty poor.
Special sub ohm testers usually use a 4 connection meter. two leads apply a constant current, and two pick up the developed voltage.
I used my adjustable constant current lab supply, set to produce 1A CC.
This current through the sub ohm cable wires will develop 1V/ohm, so the cables actual resistance can be measured with 0.001ohm accuracy. The voltmeter will read 220mV for the 0.220 ohms.
Since the current is constant, and the current connections are separate from the measuring connections, the accuracy is very good.

Power semiconductors

Power semiconductors
Some huge power semiconductors
A beautiful assortment of power semiconductors.
How does 300A @ 1200V half bridge sound, yikes that is 360,000 Watts of power.

Put your exercize to good use?

Like most Americans I eat too much and do not get enough exercise. I also watch TV too much.
I modified an exercise bike to produce electricity. The electricity runs a tv, radio, lights, fans, to use the power that I am generating. Old car alternator, with a a small battery to get the field excited to start the generating. 250 Watts is a lot of work.
For a light workout pump during the show, and rest during the commercials, For a full workout watch a DVD movie and pump the whole time.
Put your exercize to good use?
Dont stop till the commertial

Some uses of laser pointers

We all should have a couple of laser pointers sitting in the "used to be cool toy box" There are many uses for those lasers other than the usual pointer application.
Detecting things:
I have used them for generating an electrical signal when detecting things. I needed a flow meter to detect the flow rate of the heat exchanger for my solar heating system. To buy a unit with high accuracy, and a readout, was in the several hundred dollar range. I found this cute German made home water meter for less than $100. It only had one pulse output for every gallon, which was not sufficiently accurate to measure the sub gallon per minute rates that were sometmes necessary. I mounted a laser pointer so that it shined through the notches on the rotating disk that was right on the flow turbine, so it turned hundreds of times to each gallon of flow, and gave multiple puldes per revolution. I mounted a photodetector in a blackened tube, and glued a lens on the front of the tube. The detector assembly was focused on the notches of the rotating disk. and was able to generate a pulse stream for each rotation. This pulse was buffered, amplified and converted to a digital pulse that was read by the controlling computer to regulate the speed of the pump to produce a constant flow rate.


Some uses of laser pointers
Detecting a rotating disk