timing circuit

[chancer]

I'm trying to design a timing circuit that will flash a light. I believe i can just use 555s? I want the light to flash for x amount of seconds then stay off for y amount of minutes then flash again etc over and over until power removed. I want to be able to change x and y so am i able to use 2 small pots to control x and y ? Am having trouble figuring how to connect 2 555s (or do i need 3 for the flashing or pulses to the light?) Any help/suggestions/pictures would be great.

 

[meowth08]

Hi,

If you are really inclined to using a 555 timer, you need only one 555 configured in astable mode of operation. However, I don't know if it can support a very low duty cycle since you need an on time for the light in seconds only while off time in minutes.

You can refer to page 9 of the datasheet in this site.
https://www.electro-tech-online.com/custompdfs/2012/05/tlc555.pdf

Regards,
meowth8

 

[Reloadron]

You could possible use a gated flasher circuit. The gate would be driven by another simple oscillator using the same CD4011. So the gated flasher is the LED flash rate circuit and you gate it using another similar circuit with a longer time constant. Single chip and a few parts.

Ron

 

[chancer]

I'm open to any design ideas to accomplish it. Obviously the simpler the better. I just thought a couple 555 could do it. As far as the duty cycle on, it can be 10-30 seconds+. If the output to the light is pulsed, I'm assuming i could vary the lights on pulse if the on time wasn't to my liking ? Thanks for speedy reply.

I don't know what I'm talking about. I just know what I need.

 

[chancer]

this CD4011 sounds like a very versatile chip. would it just require two of them ? one for the flasher and one for the two timing cycles ? i think i see how i can vary the on/off flash pulse in the diagram of the link you gave me. Varying the bleed resistor that's in series with the diode ? i feel like a kid again trying to figure this out.

 

[Reloadron]

The CD4011 is a quad chip so you only need a single package. Here is another example. If we look at the gated oscillator example that is your LED circuit. Now also looking at that same circuit if pin one the enable line is tied to pin two it becomes just an oscillator (less being gated). The 100K resistor would become a pot, maybe a 50K pot in series with a 50K resistor. That becomes the timing pot.

There was also a thread recently about pumps and forum member Alec did some really great timing circuits in that thread. The thread exceeds 35 pages last I looked but you also may want to look over some of the timing circuits Alec was kind enough to provide. I am at work so in and out of here during the day.

The CD4011 is just an example, other chips can be used. I did not actually run these circuits in a simulation. I wanted simple, quick and low parts count to suggest.

Ron

 

[WTP Pepper]

Use a 4538 Dual monostable. Get each one to trigger the other in an astable configuration. I will post rough schematic when I get time, but you could start by reading the datasheet.

 

[ChrisP58]

If you don't mind writing some code, it would be easy to do with a uController. The PIC10F222 is a 6 pin part that would do it all. If you don't need to adjust the timing in the field, the slightly less expensive PIC10F200 would work.

 

[chancer]

thanks for the links Reload. it looks like the single led gate (for flashing) combined with the repeating timer (2) by Ron might do the trick.

Thanks WTP i would like to see a sketch when you can post it of how the 4538 can accomplish this.

Chris im not entirely against some programming. I like the idea of one chip does it all. How would this be accomplished? what would be needed to program it ? not sure i have the tool/equiptment to do it. Can you elaborate on exactly how i could make the PIC10F222 do what i want ?

Im amazed at the entirely different ways this this task can be accomplished. Almost like windows operating system. 3+ ways to do anything. lol

Thanks for all your help !

 

[ChrisP58]

Set up your two pots between gnd and the 5V power rail. Take the wipers of the two pots into two pins of the uC that are configured as analog inputs. Use the ADC fuuction in the uC to convert the variable voltages into numbers, X and Y. Use those numbers as counter trip points.

Counter one will be blink rate. 1/2 second on, 1/2 second off, or whatever you need.
Counter two is how many blinks. This is set by X
Counter three is the 'no blink' period. This is set by Y

You can get rid of the pots if you can define X and Y as constants that are fixed at programming time. They can be changed by reflashing the chip many times.

For writing code, I use Microchips MPLAB. It also has a software simulator for testing code before loading it into hardware.

Microchips PICkit programmers are probably the easiest to use, as they integrate into MPLAB.
**broken link removed**

For more on Microcontroller programming in general, dig through this sub forum. https://www.electro-tech-online.com/forums/microcontrollers/