Making UV LED exposure unit - looking for min:sec 12V timer switch

Thread Starter

Clay H

Joined Mar 5, 2019
I've searched the forums here and it seems that most of the timer discussions center around a 555 programmable timer or other more elaborate needs. I am looking for a simple, inexpensive countdown timer that will allow a user to enter minutes and/or seconds and then hit start to light up the LEDs and then close the circuit when the time has elapsed. There seem to be a lot of programmable timers out there that are vast overkill for a small project like this. Anybody have a source for a readymade simple 12V circuit timer/switch? Even something with just seconds and and up or down arrow to set the desired time would work. Looking for simple and cheap.


Joined Jan 29, 2010
hi Clay,
Welcome to AAC.
I use these timer modules, low cost.

Working modes selection: after power on, long press K1 for 2s, later into the selection of modes: P1~4.
P-1: Monostable trigger delay, a signal to trigger relay, time is up, the relay disconnect;
P-2: A signal trigger and countdown begins, T1 seconds after, the relay open T2 seconds, then close;
P-3: Open T1 seconds, disconnect T2 seconds, infinite loop. Users can set the relay time T1 and T2;
P-4: The relay opens when a signal triggers, when the trigger signal disappears, digital countdown begins, and the relay closes when the time is up.

Working Voltage: DC 12V / DC 24V (Optional)
Timing Range(Settable): 0.1~99.9 seconds; 1~999 seconds; 1~999 minutes
Signal Voltage: DC 4~20V
Output Capacity: Can Control the Load within DC 30V 10A or AC 220V 10A
Static Current: 20mA
Working Current: 50mA
Working Temperature: -40~85°C


Joined Jan 29, 2010
They have an isolated set of SPCO relay set of contacts.
The push buttons are a little 'intuitive' , could be 'letter coded' better.