Help for designing simple 9VDC, adjustable 0-10 min timer with led - Page 1
Forum section: electronics / projects

author: Osku1983
author_rank: Newbie
timestamp: March 27, 2025, 06:21:24 am
content: Hi,I have a problem and almost zero skills with electronics. Hope someone could help me with this.I need a small 0-10 min timer with only 9VDC battery for power supply. User must be able to adjust the timer with potentiometer (or screw driver). When the time is passed, led light must go on ("lighthouse" -type led light that is visible to all directions). The timer is resetted with one button and the timer will start all over again immediately. On/off switch must be included to save battery.ps. Mechanical egg timer is not enough at this point.

author: Zero999
author_rank: Super Contributor
timestamp: March 27, 2025, 01:52:54 pm
content: Perhaps something like this. It might need to be modified for 9V, but that's just a matter of changing the relay to a lower voltage one.http://www.velleman.co.uk/contents/en-uk/p203_k2579.html?srsltid=AfmBOoos5zVDpCNQy0g5sqZygbVjWrGHDOgRKptP1bxsIhfMDv6cl0Oy

author: themadhippy
author_rank: Super Contributor
timestamp: March 27, 2025, 02:41:12 pm
content: QuoteOr ditch the relay and D1,tweak the value of R7 to suit your existing LED thats fitted in place of LD1

author: Peabody
author_rank: Super Contributor
timestamp: March 27, 2025, 03:10:11 pm
content: Or for a somewhat more elegant version, you could use a microprocessor like the ATtiny85. It has five GPIO pins. You could use two pins as inputs from a rotary encoder, a third pin for the encoder's push-button, and the remaining two pins to drive an 8-bit shift register which in turn would drive a single-digit 7-segment display and the LED output. This version would let you set the time accurately, and it would display the current setting. And you could implement countdown flashes or other features if you like. The Arduino forum might be a good place to get help with this version.

author: ledtester
author_rank: Super Contributor
timestamp: March 27, 2025, 04:09:10 pm
content: Look for a "relay timer" like this:https://www.amazon.com/DROK-Controller-Delay-off-0-01s-9999mins-Switching/dp/B07DFT2WDS/With a few electronic parts you could make your timer with a C005 timer module. See for more info:https://westsideelectronics.com/delay-timer-ic/Available (for cheap) on Aliexpress and Amazon.

author: TomKatt
author_rank: Frequent Contributor
timestamp: March 27, 2025, 04:24:41 pm
content: Quote from: ledtester on March 27, 2025, 04:09:10 pmBoards like these often solve problems at prices cheaper than you can build yourself... Sometimes I like to build something for the sake of learning, but if some element just needs solving for the bigger picture I admit to just buying a cheap module and moving on lol.

author: Osku1983
author_rank: Newbie
timestamp: March 28, 2025, 05:51:36 am
content: Thank you all for your input with this case!I have an extra Siemens LOGO! logic and this could be easily done with that but I have been asked not to do this with hard wiring. I think I will suggest the LOGO! after all because it is just so much easier to me. I also need 8 pieces of this timer so it may even be cheaper to make this with LOGO! + leds + push buttons and only make hard wiring for each indicator/reset locations.I will check the relay timer options first though.ps. ChatGPT suggested ATtiny85 also!

author: Zero999
author_rank: Super Contributor
timestamp: March 28, 2025, 11:15:01 am
content: Quote from: Osku1983 on March 28, 2025, 05:51:36 amWhy didn't you say you needed 8 channels before?I would definitely recommend a PLC. The Siemens LOGO! is a decent enough solution. The only issue is it's designed for 12V. If you only have 9V, then you'll need a boost converter.