Advice for my disabled son please (timer for rotary film processor)

He is building a rotary film processor

He wants to include a TIMER (we have no idea.
Bought these


and


It needs to be able to start, run for a set time say 30 minutes and stop, 12v, HELP PLEASE, happy to return in wrong and buy the right thing, as there is NO wiring help we are stumped, AUTISM

Thank you

We need to know the electrical requirements of the film processor. Can you post them please or provide a model number so we can trace the specification.

Diolch yn fawr,
Brian.

My son designed it simply aa battery power supply 12v out to a on off switch, then to the drive in the image, the 12v battery pack is shown on the base

Help him work through "requirements" first in an orderly process. This is always a useful skill. It informs selection of approach.

Electromechanical approaches may be more intuitive / accessible, and could be upgraded later. Like a windup kitchen timer and replace the "dinger" with a contact pair. Easy hand tools and soldering skills builder, and any shortcomings become Phase 2....

Scrounging parts is also a key hobbyist skill set unless said hobbyist is made of money. Get him to "see" the problem and let him "see" solutions that lie around him.

I added notations for the module that appears easiest to understand. Apparently the module runs on 12VDC. Probably less than 1/4 Amp of current. This can be wired directly to your 12V battery pack. Observe polarity. (Most likely the module is designed to be plugged in 24/7.)

It closes a relay labelled for 20A (14VDC or 120VAC). It's adequate assuming the appliance doesn't draw more than 20A.
The relay makes or breaks one of the wires between appliance and 12V pack. Polarity does not appear to be labelled at the relay connector, therefore it probably does not matter. (Relay coil is electrically separate from relay contacts.)

Screws hold wires in place.

Spend time working the buttons to discover how to set 30 minutes On-time. I suppose you wish to press a button, then forget it.