5 Minute Timer - Page 1
Forum section: electronics / projects

author: dudester_was_here
author_rank: Newbie
timestamp: March 11, 2025, 07:47:05 am
content: Hi,I need to power a 5V lighting display for 5 minutes after a momentary button is pressed.Current draw will be about 240mA.I have a very tight space 50mm x 50mm x 7mm high !!!I know 555's are not ideal at these time spans...Happy to use a micro like an ESP32 (that will fit) but cant fit a relay in this space...Any idea's?

author: PCB.Wiz
author_rank: Super Contributor
timestamp: March 11, 2025, 08:17:22 am
content: Quote from: dudester_was_here on March 11, 2025, 07:47:05 amMaybe the HEF4541, a 2^N binary divider monostable, designed for long times to about 1% ballpark.

author: dudester_was_here
author_rank: Newbie
timestamp: March 11, 2025, 08:20:56 am
content: OK, thanks.Never used those, can you point me in the right direction for a schematic?

author: Zero999
author_rank: Super Contributor
timestamp: March 11, 2025, 08:35:41 am
content: https://www.ti.com/lit/ds/symlink/cd4541b.pdfhttps://www.codrey.com/electronics/cd4541-programmable-timer-ic-cheat-sheet/https://www.electroschematics.com/0-3-seconds-to-10-hours-timer-relay/

author: PCB.Wiz
author_rank: Super Contributor
timestamp: March 11, 2025, 08:39:41 am
content: Quote from: dudester_was_here on March 11, 2025, 08:20:56 amThe TI and Nexperia data have partial schematics.It is a R.C.R oscillator, with graphs, and you wire phase to set polarity and mode for one-shot.Pick either a PMOS or NMOS switch for your 5V 240mA load.

author: Picuino
author_rank: Super Contributor
timestamp: March 11, 2025, 08:51:41 am
content: Perhaps the CMOS part ICM7555 (similar to NE555) can do the job?https://www.nxp.com/docs/en/data-sheet/ICM7555.pdfFEATURES:* Timing from microseconds through hours5-to-30-minute-timer-circuit-7555/

author: Picuino
author_rank: Super Contributor
timestamp: March 11, 2025, 09:01:32 am
content: Although this could be a good time to learn how to use microcontrollers such as the Attiny85 or the smaller PICs.https://www.instructables.com/How-to-Program-an-Attiny85-From-an-Arduino-Uno/

author: dudester_was_here
author_rank: Newbie
timestamp: March 11, 2025, 09:03:46 am
content: Quote from: Picuino on March 11, 2025, 09:01:32 amIm fine with micro's'(digital), would much rather do it with a micro actually but I cant fit a relay in the space

author: PCB.Wiz
author_rank: Super Contributor
timestamp: March 11, 2025, 09:14:59 am
content: Quote from: Picuino on March 11, 2025, 08:51:41 amThat’s very hard to test, and has poor tolerance.The 74hc5555 would be a better choice, but Nexperia have EOL on this.

author: fchk
author_rank: Frequent Contributor
timestamp: March 11, 2025, 09:17:31 am
content: Quote from: dudester_was_here on March 11, 2025, 07:47:05 amSwitching 5V 500mA low side (minus is switched, plus is permanantly on +5V:https://www.ti.com/product/de-de/TPS2041B/part-details/TPS2041BDBVRUse a 10k Pullup on the Enable pin, leave OC open.Timing:A small PIC should do the trick:https://www.microchip.com/en-us/product/pic10f322Available in 6 Pin SOT23 package.Power, 100n between VCC and GND, maybe an additional 10u, and thats it.

author: Zero999
author_rank: Super Contributor
timestamp: March 11, 2025, 09:17:40 am
content: Quote from: dudester_was_here on March 11, 2025, 09:03:46 amDon't use a relay. Use a transistor. There are plenty of MOSFETS which can switch 240mA. For example, the ZVN4306AV is a though hole TO-92 part and is more than adequate.https://www.diodes.com/assets/Datasheets/ZVN4306AV.pdf

author: Picuino
author_rank: Super Contributor
timestamp: March 11, 2025, 09:24:34 am
content: An 8-pin micro is just as large and requires fewer external components (capacitors and resistors) than a 555. It is actually smaller.

author: Whales
author_rank: Super Contributor
timestamp: March 11, 2025, 10:00:56 am
content: It looks like you're assuming that relays are a microcontroller thing, and that if you don't use a microcontroller then you don't need a relay. This isn't true at all.Your timing source can be almost anything (a micro, a 555, a CD4541, etc). Your 5V output control can be almost anything (a single N-mosfet, a single relay, etc).

author: dudester_was_here
author_rank: Newbie
timestamp: March 11, 2025, 09:54:31 pm
content: Quote from: Whales on March 11, 2025, 10:00:56 amI was, your right.Rethinking my ways now.Thank you

author: dudester_was_here
author_rank: Newbie
timestamp: March 11, 2025, 10:27:39 pm
content: Quote from: fchk on March 11, 2025, 09:17:31 am

author: fchk
author_rank: Frequent Contributor
timestamp: March 13, 2025, 10:41:12 am
content: Quote from: dudester_was_here on March 11, 2025, 10:27:39 pm

author: PCB.Wiz
author_rank: Super Contributor
timestamp: March 14, 2025, 01:11:12 am
content: Quote from: fchk on March 13, 2025, 10:41:12 amOr, there is this new entrant in the small MCU stakeshttps://edacafe.com/nbc/articles/1/2123845/TI-introduces-world-smallest-MCU-enabling-innovation-tiniest-applications16KB of flash; 12-bit analog-to-digital converter with three channels; six general-purpose input/output pins; and compatibility with standard communication interfaces such as Universal Asynchronous Receiver Transmitter (UART), Serial Peripheral Interface (SPI) and Inter-Integrated Circuit (I2C). Integrating accurate, high-speed analog components into the world's smallest MCU gives engineers the flexibility to maintain the computing performance of their embedded systems without increasing board size....Starting at US$0.16/1k - comes in WCSP, and also SOT23-8 and SOT23-16 and DFN8 (2x2mm)The MSPM0C1104 LaunchPad™ development kit is available for US$5.99 on TI.com.For timing, these new parts have better calibrated RCOSC than older ones, and a lot more flash and peripherals. (eg 12b ADC)There is no crystal option on the MSPM0C1104, but I see it has a HFCLK_IN option, on all packages and LFCLK_IN on some, for more precise timing.They are not 5V parts, however, which may limit their applications, parts like EFM8BB50 work 1.8-5.5V and come in DFN12(2x2)These EFM8 parts have a low tempco LFOSC, well suited to timing.