I have three separate lighting controllers which all have a programmed sequence of slowly dimming lights up and down. These are wired in parallel as I want to be able to turn these on and off with a single switch at the wall (for aesthetic and ease of use reasons).
When switched on at the wall, I want to introduce a delay in when each lighting controller receives current. So the circuit is switched on, and the first lighting controller receives current immediately. After approximately a 1 second delay, the second lighting controller receives current. Then, after a further 1 second approximate delay, the third lighting controller receives current. This will produce an effect where the lights are no longer operating in sync with each other. To be clear, this delay would be a one-time thing each time the circuit is switched on at the wall – it does not need to continue to happen during operation.
The delay does not need to be especially precise or especially repeatable.
I'm new to learning EE, and I'm wondering if there's some off the shelf component or product that will fulfill this function? Ideally I am looking for something which is small in size.
I am working with an experienced electrician to build this device but I would like to design it myself as a learning experience. Please let me know if I need to provide any further information.
Best Answer
simulate this circuit – Schematic created using CircuitLab
In schematic above, you can choose to employ switch 2 (you can use a wall mains switch) or switch 1.
The values of R1 and C1 are indicative, C1 is charged to 3V in about 1 second with these values, which should be around the threshold voltage of NMOS M3. You should base the exact values on the threshold value of M3.
When M3 is triggered, it turns on M2, which turns on the relay. The relay turns on light controller 1 and the second 5V adapter.
The same circuit should be connected to this second adapter, so it turns on light controller 2 and adapter 3 after 1 second delay. And same circuit to adapater 3, which turns on light controller 3.
Most important of using a timer based on a R and C is that the capacitor is not being sourced or drained by something else rather than by the intended components (at the node indicated by the red arrow).
Also still in this schematic there is a leakage current, which draws away charging current: the gate source leakage current of M3. Although it is probably in the order of nA to uA, it may matter as the charging current is in the 0..10uA range. (With the edit, D2 also has leakage, but is the order of nA).
EDIT If the discharging of C1 would be an issue, you could add a low leakage diode D2, which discharges C1 through R5 when the 5V adapter is turned off as shown in the circuit above.