Yes, that circuit will always draw power, not a lot, but it’s not 0. Depending on the on or off state, either Q1 or Q2 is conducting to hold that state. Current draws are miniscule, with the 10K and 470K resistors used for biasing, but again, it’s not 0. It will take a long time to drain the batteries when off.
Can’t really be avoided, the only zero current draw option is the latching reed switch (and after a long enough time the bias magnet would loose enough of its magnatism to not work any more - like old motor magnets get weak. But we’re talking 40-50+ years here, hardly worth worrying about.
As for this circuit, I didn’t look up the limits on the BC547 to see what kind of load it can handle. Probably NOT 5-6 30ma light bulbs.
BTW that’s a great site with lots of information and useful circuits. The section on H-bridges, that’s how DCC decoders drive the motor. ANd there are a pair of nice simple CDU power supplies for those using twin coil switch motors.
Just picking this electronic stuff up mostly by teaching myself over the last 40 years, so still learning. I bought that Forest Mimms book from Radio Shack when I was a kid and understood about a tenth of it, [:^)] but came back to it later in life and it made more sense. Anyway, I’m rambling now.
I wondered myself if you would advise possible adjustment of the resistors.
I’m also wondering if the 2222 would need more power to turn on? Changing the charging resistor or the cap?
I’ll have to look closer at the datasheets. While those are helpful, some of the specs are like a foreign language, again [:^)]
It’s a circuit I want to breadboard and take to a proto-board once it’s solid.
If I have issues I might look you up again.
Thanks for the know-how as always!
Thinking about latching reed switches;
If one took a normal reed switch and carefully wrapped and secured a coil of magnet wire around the tube then fed the coil from the reed switch through an appropriate resistor, when you used a magnet to initiate the circuit, would the coil be able to latch the relay until an opposite pole magnet was used to open the circuit again?
That might work, but getting the right number of turns so the coil wouldn’t draw too much power might be tricky. The other option would be two reed switches and a relay wired to latch, one reed switch bypaases the latching contacts to pull the relay in, ther other would be a NC reed switch which would interrupt the relay power and allow it to drop out. Magnet to the frotn of the car turns on the lights, magnet to the rear turns them off.
As others have pointed out you are looking for a latching magnetic reed switch. I have used them for caboose interior lighting with great success. An Austrian company used to sell them through Walthers but they haven’t been listed in Walthers for years now. There must be sources because they are used today for passenger lighting in some of the high end passneger car runs.