I want to put a push button switch in me basement that will turn of the dehumidifier for 5 hours, or so. I’ve found a basic circuit that will turn a light on for 30 minutes. Obviously I need to connect to the other input of the relay to turn off instead of on, replace the relay with a heavier duty one, and change the timing.
My question is, since I have no need for the warning lights, can I safely remove IC1A, IC1B, R1 and D5 from the circuit? What about the connection from pin 16 of IC2 to D3?
Also, how does one calculate what affect R4 and C4 have on the timing of the circuit?
Forgive my ignorance. My circuit design knowledge is weak, and my confidence in these matters is a bit low.
You can safely remove IC1 (note - A and B are just two gates from the same chip) R1 and D5. You need to keep the connection from IC2 to D3 since this is the reset connection to IC2 and starts the whole timing operation.
R4 and C4 are used with internal gates on the 4060 to make an RC oscillator. The datasheet for the 4060 makes it a bit more obvious. The RC time constant is going to dictate how fast the change of state feeds back into the first gate and flips it, which determines the oscillation frequency.
The one you linked to is a repeating interval timer, and continues repeating as long as the input voltage is applied. This one looks promising, except I would need to continuously keep the input voltage applied, and interrupt it when I want the humidifier off. Seems a bit wasteful to me (and less fun than building one).
MrFantsyPants, why don’t you tell us your overall goal in this project? Do you just want to turn off an appliance for a few hours every night? If so, wouldn’t a simple Sears appliance timer (like David Simmons’ link) do the trick?
Or do you want to turn it off just to avoid too much dehumidifying? If so, even cheap models of new dehumidifiers include humidity sensors and will shut it off when the room reaches your desired setting. I have mine in the basement set to 40% year-round, and right now it is off automatically.
WWGrainger has a couple of possibilities. Search by item number for 5JJ50. It is a multi-function time delay relay with contacts rated for 10A resistive and 1/3HP with a range of 0.1 sec~1705 hours. You’d want ‘Off Delay’ function.
You could also use item number 4WZ52 to control the coil of a relay with fatter contacts, such as 5Z484. Note that sockets are required for both relays, and you must have a business account (or a friend who does) to purchase from Grainger.
The dehumidifier is in what is about to become our new movie room. If I just turn the humidifier off during a movie, there is a good chance I’ll forget to turn it back on, then along comes the damp.
I think I might try building it myself. Anyone know a good place to by components (ICs, relays, etc) online. Google search brings up a vast array of really crappy places.
Might I suggest you use industrial electrical control components? It’s not the cheapest option, but it will be safe and reliable.
Allen Bradley makes a wide range of industrial relays and timers (standard, time-delay, latching, solid state, etc.). I don’t have time to peruse their site, but perhaps they have a time delay relay that meets your requirements (N.C. contacts, 10 A, etc.). Another option would be to use an inexpensive N.O. timing relay that drives a contactor w/ a N.C. output.
Digikey has a nice parametric search tool; Mouser sometimes has cheaper prices on lower-quantity orders. I’ve dealt with both and was pretty happy with each. Neither has a minimum order.
For used/surplus stuff, I’ve had good results on several orders from:
www.mpja.com (they have some great deals on power supplies)
and I had a positive experience buying a NOS switchmode power supply from these guys:
I’ve never ordered from him, but I’ve read positive things about this guy when it comes time to have your PCB manufactured:
www.olimex.com (he also has PIC and AVR programmers for WAY less then the official price-- www.sparkfun.com is his US reseller for those. Ordered from them succesfully)
Speaking of PCB’s, the best “amatuer” PCB design program seems to be Eagle:
Have fun, and don’t kill yourself! If you’re going to power your circuit from a switcher, an isolation transformer may be a good investment (look on ebay–I got a like-new 1KVA unit for $40).
Just a suggestion. Instead of a timer, use a passive infrared sensor of the type that turns a light on when someone trips it. Use the output to power a relay that cuts the power to the dehumidifier. Then it’ll turn off whenever anyone is in the room, no button pressing or timers required.