Digital Timer controller Help

Thread Starter


Joined Oct 26, 2004
Just wanted to know how hard it would be to build an electronic digital display that would turn on and off a 120 v appliance that could be set at half second intervals from .5 seconds to 10 seconds and repeat this cycle over and over.
It must be highly durable.I have no electronics background and I am actually looking for someone to build this for me if it works for the machines that I want to use it on and if the price is right I will need several of these units built.Complete details can be supplied .I am a budding enterpenuer that needs some help.
Please e-mail or reply to the group.
Thank You for your time.


Joined Oct 12, 2004
1. Maybe you could just briefly describe what human-device interaction is required. By "display" are you talking about some multi-digit display to show the current interval value - like, "0.5" through "10"? Would it just be something like two buttons, an Up Arrow button to increase the interval and a Down Arrow button to decrease it (in .5 sec intervals), and the display?

2. From your description, it looks to me like you have a fixed "duty cycle" - meaning that if the interval is set to 3.2 then the device would be ON for 3.2 secs and OFF for 3.2 secs. Is this so? Would you ever need the ON/OFF times to be different?

3. Controlling the 120 v device is simple. The human interface is the complicating factor. Anyway, owing to that human/control interface factor, it looks like a PIC micro-controller based application to me.



Joined Jan 22, 2004

i could not get the picture, what's the purpose of the digital display? is it just to show that the machine is on or off? if so, a flashing LED indicator will suffice.

what kind of machine do you intend to be controlled?

do you intend to vary the time interval electronically according to need because you were mentioning a 0.5s to 10s time interval. :unsure:


Joined Oct 27, 2004
Here's a Shot.

The Frequency (.5 Seconds - 10 Seconds) is controlled by R3 (Variable resister controlled by a knob)

This changes the frequency of the clock pulse. The clock pulse then triggers a relay to activate the 110v System.

Does the duty cycle need to be 50%? If so, you will need to do some component calculation on the 555. You can use this website:

The labels on the attachment might not be correct. I just slapped the schematic down real quick so you have a visual.

Good Luck!


  • 10.1 KB Views: 48