K2579 stop/start problems

I am having problems which seem to be attributable to oversensitivity of the ‘start/stop’ part of the circuits. 1. Upon switching on the mains supply the relay o/p closes by itself (unacceptable in this application). 2. The operation of the load (a 12V solenoid) directly from the o/p relay by activating the ‘start’ button (wired remotely) causes the ‘stop’ to work. 3. Feeding the o/p relay into a second, high current, relay (even with no load on that one) thus causes a rapid alternation between ‘stop’ and ‘start’, so that this relay ‘chatters’. 4. Operation of a completely separate circuit (also a 12V solenoid), starts the timer o/p as well; the only link seems to be that the wires of the two circuits are near one another in places.

I have tried using a separate power supply (a Velleman K1823) and transformer for the timer; also a completely separate supply from a battery charger, all without success.

A separate issue is how to get the time adjustment sensitive enough to time accurately within the range 5-20 seconds? I have tried lowering the capacitor C2 to no avail.

So…I would be most grateful for any suggestions to enable me to solve this problem, which I realise is not new to the forum, either by changing the values of components, adding new ones, or failing all else, use of a different circuit altogether.

Many thanks in anticipation of your assistance.

If the application is that critical, we’d recommend the K8015 instead of the ‘basic’ K2579 kit.
If you use the K2579 kit, most likely the problem is caused by the fact that the buttons are removed from the PCB and poor supply filtering.

Can you help with the second part of this question please, I have a need to set the intervals to 4 seconds, and I have been unable to set the trim pot to a value that will achieve this.