I was interested on the New surplus relays that goldmine-elec.com has recently acquired. BTW, these may be sold out and no longer available soon.
I noticed that the operating power is only 10 to 13 milliwatts, which is extremely low. But the figures don’t make sense. Ten milliamps would go through 300 ohms, not 3000 ohms. I’ll have to check the resistance when I get them.
I thought that this might be lower than the amount of power dissipated by a forward biased diode when current is passing through it. Say, for instance I had a solar panel outside and I have to use a diode in series, a 1N5817, for instance to prevent current from flowing back into the panel at night. Say the panel puts out 1/2 amp (contacts rated maximum). A half volt drop across the diode at 1/2 amp is 1/4 watt or 250 milliwatts. In this case, the relay would save save over 200 milliwatts. The relay has to turn on and off only once a day, so its lifetime would be very long. The speed makes no difference. This seems to be a good use for them.
I also thought the relay would work well on the output of a low power Joule Thief. I could put a 1N4148 diode and a 10 uF filter capacitor on the JT output to turn the output into DC. The relay could then be operated by a voltage less than 1 volt DC. A red LED might be put in series to indicate when it is on. The relay could be rewound with less turns of wire, but this wire is so fine that it would be difficult and tedious to do it, not to mention that the relay is in a sealed metal package.
This relay can be used, along with a snubber diode, on the output of a microcontroller. It will give very good isolation between the microcontroller and the external circuit it is controlling. Transistors are typically used for this. But if the transistor fails, the high power could damage the microcontroller. But remember, the electromechanical relay is much slower than the transistor.
I’ve thought of other uses for this low power reed relay. I have to emphasize low power, because most relays take a lot more power than this to operate, and can be used in higher power circuits. But lower power relays are uncommon and useful for low power circuits.