F/F Circuit

Don't know your application how ever.. they make latching relays..

Get one with a DPDT set of contacts. One pole will be used to signal the direction to switch a monostable type circuit composed of 2 transistors with a few minor components added. The relay has 2 coils and thus are used as the collector load side resisters for the monostable circuit.

The set of contacts you'll be using will have a resister connected to the Center Pole while the outer contacts, each being connected to the base of a transistor.. The idea is to create a slight offset so that the monostable will favor a side. Because there is induction involved here, the circuit will be fully on position before the coil even starts the create current. So this means when the contacts do open to change sides, the unloading effect will not alter the operation.

That will retain the last position with out the use of constant power. Of course, you didn't specify the working cycle rate you expect to get. These relays are mechanical so take it from there.

This is an old trick I have used for years for alternating a state from a single source point for basic stuff.

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The professor wants a small box (3"X5") with 4 components on the front panel An on-off power switch to turn off a 5v to 12v power supply. A green LED located near the switch to indicate power on. On the left side of the box there will be 2 LEDs, 1 blue and 1 red. When the power if off = no lights. When the power is turned on the green and blue LEDs will light. The next power on the green and red LEDs will come on, etc., etc,.. Next semester we will go further with this but for now, that's all I can say. Still want to help?

west

A 2D box in a 3D world could be difficult. I have to ask my distributor, if they have some 2D parts.

Do you want that we serve up the homework on a plate to you? Which one of the many suggested solutions doesn't help you?

I would do it with a microcontroller, because there are ones with integrated power-on-reset and oscillator, like the MSP430F2111 for $2,25, so you have to write just about 5 lines of assember code to solve this task. The datasheet says the integrated flash has a life time of 100,000 erase/program cycles, so this should be fine, unless your professor wants to switch it more often :-)

For the voltage regulator you could use something like the LP2981 for $0.80 from Digikey for 3.3V output voltage, which works then for input voltages up to 16V and down to 3.5V. All parts would fit in matchbox.

Or the PIC12F629

Only $1.75 a piece at Digi-Key, and has 1,000,000 EEPROM erase/program cycles. Comes in 8 pin DIP package, so it's easy to solder for beginners. A built-in status register tells you the reason for the reset, so you can see if it was just powered on. It also has a wide

Looks nice.

Looking at the datasheet, there is a patent cited:

They are kidding, right? They can't patent the "invention" that a microcontroller with n bits data bus has n pins, can they?

Frank Buss snipped-for-privacy@frank-buss.de posted to sci.electronics.design:

No, just some other tiny aspect of the device.