How to use these common Chinese timer modules

These modules are very common on the usual online retail sites, but the information on using them is very vague. So here's a guide to using them.

The modules can be powered by a micro USB cable or a DC supply of 6 to 30V. In reality I recommend using between 8V and 12V if the relay is going to be energised much, as the onboard voltage regulator is a simple linear one and will dissipate the dropped voltage as heat. The combined load of the display and relay is about 100mA, so that will result in a lot of heat at higher voltages.

The trigger input is opto-isolated and can be between 3 and 24V. There is an option to add a soldered link to bridge the trigger and circuit ground if desired, or they can just be linked with wire in the terminals if the module power and trigger is coming from a common supply.

The output terminals are volt-free and wired directly to the relay with beefy tracks. There is a common connection and then a normally open and normally closed contact that change state when the relay is energised.

The unit has four buttons to change its settings.

The STOP button has three functions:- A brief press toggles between ON and OFF to enable or disable the relay output. That allows you to test or adjust the module without powering a load. During programming it can change the position of the decimal point to allow 10th second or 1 second increments. If all three decimal points are lit, the timing is in minutes. If the button is pressed for 5 seconds and then released it toggles between 0-d where the display is on continuously and C-P where the display sleeps after 5 minutes.

The SET button will display the timer settings if pressed briefly. If SET is pressed for 5 seconds it enters setup mode. Initially it will display the mode as P1.X to P-4 After the mode is selected using the up/down buttons the SET button can be pressed again and will then step through the available time settings as follows:- OP is the desired on time for the relay. CL is the desired off time for the relay. if used in the selected mode. LOP is the desired number of cycles from 1-999 or select - - - for continuous. Use the up/down buttons to adjust the values and the STOP button to move the decimal point for tenths of seconds, seconds, and minutes (three decimal points lit).

To exit the setup press and hold the SET key for 5 seconds. The unit will reset, show the mode and then run.

Here are the modes:-

P1.1 - trigger input causes the relay to be powered for a fixed time (OP). It ignores further trigger inputs until it has finished its timing cycle.

P1.2 - trigger input causes the relay to be powered for a fixed time (OP), but can be retriggered while timing. It will ignore the presence of a continuous trigger signal. This could work as a watchdog to detect a stalled motor, or turn off a conveyor if no moving objects are detected.

P1.3 - trigger input causes the relay to be powered for a fixed time (OP) or until another trigger signal is received, which ends the timer early.

P-2 - trigger input starts a delay time (CL) after which the relay is energised for a fixed time (OP). Another trigger turns off the relay if active, and disables triggers for the off-delay (CL) time (?). The unit ignores a continuous trigger signal.

P-3.1 - trigger input causes the relay to cycle on and off with the chosen on (OP) and off (CL) times. The cycle will be repeated as set by the loop (LOP) value from 1-999 or - - - for continuous. Another trigger while running will end the cycle.

P-3.2 - Unit will cycle as in mode P-3.1, but will start as soon as powered and ignore the trigger input. The control industry calls this a symmetric or asymmetric timer.

P-4 - trigger input causes the relay to be powered for a fixed time (OP), but can be retriggered while timing. It will stay powered with the presence of a continuous trigger signal. Could be used as a fan run-on timer.

Quite a useful little module despite its hardware shortcomings - mainly the choice of voltage regulator. The timing range is from 0.1 second to 999 minutes, making it very versatile.

Here are some typical listings on AliExpress (not a sponsor) This module:- https://vi.aliexpress.com/item/1005006151283961.html The MOSFET version:- https://vi.aliexpress.com/item/1005007045191890.html I haven't tested this version. It's only suited to DC loads and may need a diode across any inductive loads it is driving.

There are also versions available in simple cases.

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