brunnhilde's refrigerator control - part 8

 

Living within my means is always the motto. If you have very little battery bank reserve you just find ways to reduce power consumption. That is why Brunnhilde have no power hungry appliances. The roof top air conditioner does not count as it requires shore power or the generator to supply its power, and during use, any other power consumers are insignificant in comparison. Now with the refrigerator, water boiler, or the diesel furnace. They need to consume as little current from the house battery bank as possible.

It is hand to hand combat now to reduce the power consumption of the Ink Bird temperature controller for the refrigerator. I decided to reduce the power consumes by the coil of the cooling relay, by changing it to a reed NO relay. I knew I should have some in my electronics spare parts.

I found this box of ICs and in there there are a few of these long EOL Segma reed relays

they are so old that data sheet cannot be found on the web so I have to figure the pinouts; I know they are 5Vdc with 500 ohm coil

I even found some POT wires which I would use for the long cable run of the Ink Bird to the refrigerator; there must be close to 12 feet of 4 conductors needed

One thing about this 12Vdc version of Ink Bird equivalent is it has a false ground. I would not realize it had it not because I open it up and did extensive hack. The 12Vdc input goes through a full bridge rectifier in order to make it fool proof, such that the polarity does not matter. However the ground is always raised by a diode drop. Because of it rather than running three conductors to the Danfoss refrigerator compressor electronic module (two for thermistor and one for the thermostat signal T) I also run a ground to the reed relay contact.

The four conductor telephone cable serve this purpose well with the colors that make sense. Yellow and Green for the thermistor, Red for T, and Black for C. the cable is thin somewhat stiff so is really easy to feed through tight quarters and bends.

I hacked in the reed relay in dead bug fashion and secure it with 3M VHB tape so it won't go anywhere

As the reed relay is 5V I cannot just wire the coil to where the 12Vdc relay were. As I know it is driven by open drain transistor I can just wire the high side of the coil to 5Vdc of the board, and the transistor would not care. Actually the relay driving transistors are discrete NPN BJTs by the two relays. All sound good but I need to test the final mod with the refrigerator.

I save about 20mA with the reed relay hack

Since it is really hot out, I spent time doing more fabrications in the house. As I am also developing the ventilation fan for the bathroom skylight I decided that I would achieve three functions with the sole rocker light switch for the bath. It would be used to control the bath light, the ventilation fan. And as if that is not enough, I want it to control the new lighting in the closet too.

For the closet lights, the goal is to illuminate the upper shelf and as well as the coat closet and storage. There will be no drilling or cutting, and the wiring must be hidden and tidy.

testing illumination and mounting locations