JTEX
Well-known member
The Cheat: use an ATtiny chip to drive latching relays directly!
Yes, it works, it can put out enough juice, I use it every day, just as seen below. No, you don't even need protection diodes across the relay coils. The chip has them built-in. Some ATtiny chips are available in DIP packages, if you don't want to do SMD.
Here's an example from my current project, where I have to drive 3 latching relays and 3 LEDs, triggered by 3 momentary switches. The idle current consumption (with the right programming, putting the chip to sleep almost all the time) is 300 microamps at 5V, plus maybe 1mA total for the 3 LEDS when they're all on (they're very efficient). The relays only draw any juice at all for about 10 milliseconds, the time it takes them to latch. I used an ATtiny167 because I needed many IO pins, but if you have just one relay, you can use an ATtiny85.
The downside is that (just like I had to...), you'll have to teach yourself how to program said ATtiny chip (use the Arduino IDE), and you'll need to put together a thing called an ISP programmer (In-System Programming). You can easily make one from an Arduino Uno or compatible board. It can program the chip via a 6-pin header after it's already on the board, all wired up with relays and all!
I'm way too lazy to write a longer-form tutorial, but I hope this is enough to maybe spark an idea for someone.
Yes, it works, it can put out enough juice, I use it every day, just as seen below. No, you don't even need protection diodes across the relay coils. The chip has them built-in. Some ATtiny chips are available in DIP packages, if you don't want to do SMD.
Here's an example from my current project, where I have to drive 3 latching relays and 3 LEDs, triggered by 3 momentary switches. The idle current consumption (with the right programming, putting the chip to sleep almost all the time) is 300 microamps at 5V, plus maybe 1mA total for the 3 LEDS when they're all on (they're very efficient). The relays only draw any juice at all for about 10 milliseconds, the time it takes them to latch. I used an ATtiny167 because I needed many IO pins, but if you have just one relay, you can use an ATtiny85.
The downside is that (just like I had to...), you'll have to teach yourself how to program said ATtiny chip (use the Arduino IDE), and you'll need to put together a thing called an ISP programmer (In-System Programming). You can easily make one from an Arduino Uno or compatible board. It can program the chip via a 6-pin header after it's already on the board, all wired up with relays and all!
I'm way too lazy to write a longer-form tutorial, but I hope this is enough to maybe spark an idea for someone.
. It doesn't take that long though. Still, I'm hoping Alpha or somebody else will see the light and make the damn part.
Because French vs. the letter H. "Ave some happle pie. Eat it before you heat it."