simple LED with delayed start

Thread Starter

miha_s

Joined Oct 29, 2014
3
Hi everyone! I am a newbie in the world of electronics and would like to construct a simple circuit and would like to ask you for some help and advice.

I would like to build a very simple circuit with a LED light, a battery, ON/OFF switch and what else is necessary. The idea is when you turn it on, the light is off for the first week and starts blinking only in the second week.

Is it possible to do it and how would you do it?

Thank you very much for any advice :)
 

ScottWang

Joined Aug 23, 2012
7,396
1. What kind of the power supply?
2. How about the V/I of the power supply?
3. How about the V/I of led?
4. How many leds do you like to use?
5. Do you need the 7-segments led display?
6. Turn on the switch, leds are off.
7. Delay for a week. (accurate)
8. The leds are blinking. (frequency?)
9. How does the next step?
a) How long do the leds still keep blinking?
b) And the next?
10. And some other things else?
 

wayneh

Joined Sep 9, 2010
17,493
I ...would like to construct a simple circuit...
Is your goal the end product or the fun of constructing it? I ask because it may be easier to use off-the-shelf components to do this project. Like a lamp timer controlling a flashing LED.
 

Bernard

Joined Aug 7, 2008
5,784
For simple, could try 4060, 4040, C555 & FET driver for LED. Accuracy maybe a hour or so in a week. First week power drain about 10 mA h, second week 1.7 Ah, so 4 AA NiMh batteries ??
? where did this cross out line come from??
 

Thread Starter

miha_s

Joined Oct 29, 2014
3
Dear all, thank you very much for all your useful information! At least now I know in which direction to proceed... Yes, maybe should explain some details:
- in general thought of batteries, such as xr2032 3V or something similar
- the idea is that the blinking light would remind my grandpa to check in the fridge for any food going bad. When he checks, then he turns off the device.
- the accuracy isn't that important, also a day up or down does not change much things.
Thank very very much again!
 

djsfantasi

Joined Apr 11, 2010
9,151
Just a couple of ideas.

A purely hardware solution would take a clock (555), feeding cascaded counters (such as the 74HC4059 presettable counter) to count for a long time - week, and a flip flop/latch to latch the output.

If you are comfortable with microprocessors, a small one could be programmed to count for a week, timer interrupts/overflow, and turn your LED on. This would result in a small package with few parts.
 

Bernard

Joined Aug 7, 2008
5,784
Just filling in the numbers from post # 5. I used a 3.3k R & red LED to monitor times. Stage 12 of 4060 = 147.6 sec. or 2 m+ 27.6 sec. Adjusted R3, 30k pot to give this time. Note that R2 + R3 = 160k, when measured = 179k with pot at about 20k. Only 4060 breadboarded. pin 3, 555 might need to go to Q11, pin 15, 4020 to release reset on 555 at count 16777216.Pulse # 2 00001.jpg
You can use an AC adapter, 4.5 V to 6V, or batteries.
 
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