Electronics > Beginners

Project: Long Duration OFF Timer Circuit for LED's

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BergRD:

--- Quote from: sokoloff on August 20, 2018, 04:54:55 pm ---I have an Arduino and a relay board driving a piece of home automation that cycles the relay 1 minute out of every 120 minutes. Took me longer to find a USB power supply in the drawer than to write the code. (It's so simple that may be the reason why it's hard to find the code on google.)

In your case, using low power sleep mode is going to be a driving factor in the design (so you don't have to change the batteries all the time).

Have a look at pages like https://learn.sparkfun.com/tutorials/reducing-arduino-power-consumption to get a handle on sleep mode and other power conserving strategies.
If you can run the AVR directly on the 4 alkaline batteries with just a regular diode in series, you'll be better off than any design that uses a linear regulator.

--- End quote ---

Yeah, this isn't something for a relay or whatnot as it's only 2 white LED's that run off a 3 AA battery pack.  Right now you switch it on and off manual and since wife forgets she wanted something that once turned on; it would turn off after X hours (preferably 4-6 hours) so not to run through batteries quickly.  The MC or CD4060 route looks to be the most promising and since I have done very little with CMOS Logic I figured I would try to see if that sort of concept is viable.  I think it is with a single CD4060 but have none or assortment on hand.  Just haven't needed them to-date and trying to find some assortment to learn with.  Always trying to learn more and more as I go.  Thanks for the posts!

sokoloff:
If you do decide to go down the AVR/Arduino route, I'm happy to play along remotely and help (if you need it). Just send a PM or update this thread later.

It's something that I've been interested in semi-passively for a while (low power, constantly powered devices, in my case for automotive [12V and 24V nominal] applications). This might be enough to kick me over the activation energy threshold.

Jeff1946:
Another way.  Use a low voltage MOSFET, for example a NTD4970N to drive LEDS (with suitable resistor).  Connect a 1000 ufd capacitor in parallel with a 10M resistor between gate and source of MOSFET.  Use a push button switch to connect MOSFET gate to plus side of battery via a 1k resistor.

The capacitor should be a quality one so the self leakage isn't too large for the time you want.  To see if this will work charge the capacitor with a battery, then measure its voltage every hour.  Note the LEDS will  slowly dim as the gate source voltage goes below about 3V.

If you use a larger resistor in place of the 1k, you can adjust the brightness by only holding down the push button until the LEDs reach the desired brightness.

mdszy:

--- Quote from: BergRD on August 20, 2018, 05:48:47 pm ---
--- Quote from: sokoloff on August 20, 2018, 04:54:55 pm ---I have an Arduino and a relay board driving a piece of home automation that cycles the relay 1 minute out of every 120 minutes. Took me longer to find a USB power supply in the drawer than to write the code. (It's so simple that may be the reason why it's hard to find the code on google.)

In your case, using low power sleep mode is going to be a driving factor in the design (so you don't have to change the batteries all the time).

Have a look at pages like https://learn.sparkfun.com/tutorials/reducing-arduino-power-consumption to get a handle on sleep mode and other power conserving strategies.
If you can run the AVR directly on the 4 alkaline batteries with just a regular diode in series, you'll be better off than any design that uses a linear regulator.

--- End quote ---

Yeah, this isn't something for a relay or whatnot as it's only 2 white LED's that run off a 3 AA battery pack.  Right now you switch it on and off manual and since wife forgets she wanted something that once turned on; it would turn off after X hours (preferably 4-6 hours) so not to run through batteries quickly.  The MC or CD4060 route looks to be the most promising and since I have done very little with CMOS Logic I figured I would try to see if that sort of concept is viable.  I think it is with a single CD4060 but have none or assortment on hand.  Just haven't needed them to-date and trying to find some assortment to learn with.  Always trying to learn more and more as I go.  Thanks for the posts!

--- End quote ---

Seems like doing CD4060 + watch crystal + MCU would work out. Use a 32.768kHz xtal, divide it down to 1Hz with the CD4060 and use the MC to count pulses until you've reached the timing you want.

Here's an example of the frequency division circuit

capt bullshot:

--- Quote from: BergRD on August 20, 2018, 02:23:07 pm ---
Been trying to find a circuit that I could build that would bring power to the LED's and start a 4-6 hour timer to turn them off once timer hits.  555 and 556 are minutes and beyond the scope (I think) of this project so I have found a few utilizing CD4060 CMOS IC's but wanted to come to the smartest people I know, here at the EEVBLOG!  Would the oscillator/binary counter be the most logical? What of the voltage requirements?  Will it work or drive 2 standard LED's (Unsure at this point the voltage drop across them but have others could supplement).. More questions as I find info so wanted to get your input.


--- End quote ---

I second the plan to use the 4060 as the main timing element. You'll want to use some output transistor to turn on the LEDs, presumably a small MOSFET, since a standard 4000 CMOS chips cannot drive the LEDs directly. Three AA batteries will provide enough voltage to supply the 4060.
 

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