Timer

I have the same problem with kids, co-workers, sub-contractors, and government agencies. They never seem to do what I want.

You're not doing much better. Input specs? Output specs? Power specs? Definition of operation? Max cost? Quantity? Timing adjustment or fixed? Adjustment ranges? Digital or analog? Accuracy?

Not a very good description. Does the timer sample the thermostat output for the full duration of 2 to 5 minutes, or does the input need to be there for the full 2 to 5 minutes? If the thermostat comes on outside of the 2 to 5 minute window, what happens to the output? What does the output do during this time? Stay on or drop out?

You probably need two timers. The 15 min to 2 hr timer enables the 2 to 5 minute timer, which then looks for an input when enabled. I have no clue if you want 12V, 24V, 117V, AC or DC to run this thing, or what manner of load, so I can't scribble a suitable circuit. A dual

DIN rail is the current fashion. Octal socket timers are rather antiquated. See if this jogs your imagination:

If you have money and want versatility, I suggest a PLC (programmable logic controller) what can be trained to do almost anything you describe with a ladder diagram.

I'm working with 120 volts. The gate is thermostat closed or 120 applied. When closed, start 2 to 5 minute timer. If set for 3 minutes, keeps contacts closed for 3 minutes as along as the gate is closed. Otherwise do nothing or drop out if gates opens. If gate is still closed do it again in 30 minutes to 2 hours, otherwise do nothing.

The load is a circulator 120 VAC.

Can a programmable thermostat do this? I thought not.

How about two re-triggerable one shots with variable delay shutoff in series.

If you're into building it yourself, here's a link to a schematic:

t I want. Descriptions on the

Ha! Just what the OP needs.

Neil S.

want. Descriptions on the

schematic:

I would have no problem building it. That's what my trade used to be.

On 10/19/2010 5:44 AM Art Todesco spake thus:

Wouldn't that be accomplished just as well and much more simply with a single 555 timer?

You might be able to do it with a single 555, but this one was already designed and was easily adjustable for each part of the cycle.