I want a simple circuit to control the rate of an LED blink.

[Bob33]

Been looking all over the internet, but can't find quite what I'm looking for.  9 volt powered preferable... can be choppy... doesn't have to be "sine-wave".... just as long as I can control the rate from slow to fast...  I'm thinking this would be a very simple circuit, but I don't know what to do.

[ExpAnonColin]

Astable multivibrators are your friends...



-Colin

[Bob33]

Cool... um.. soo... what are those trannies, and how would I control the rate of the flashing LED's?

I've found tons of those kinda schemes on the net, but none with all the parts labeled, and none 9 volt specific AND with a rate control.

[Bob33]

Also... I just need one blinking LED... not two.

[Bob33]

Like this... this looks perfect, but to adjust the rate requires adjusting the value of two resistors and a cap, but I just need a simple pot to adjust those things... hrm....



http://www.kpsec.freeuk.com/projects/flashl.htm

I see a lot of them 555 chips in various blinking diagrams.. but once again.. no rate control via  pot...

[Bob33]

On that same circuit... according to this :

http://www.kpsec.freeuk.com/stripbd.htm#example

(I'm not good with da math)

It seems that I could possibly just place a pot where one of the resistors are to effect the rate?

Possibly?

Man... I was really hoping someone would have a ready-to-go circuit laying around.

Oh well... I'll give this thread time to simmer and be back in a day or so... hopefully I'll have money to splurge on testing some ideas out by then...

[Travis]

Try the EA Trem LFO.
http://www.runoffgroove.com/eatremolo.html

The rightmost part of the schem is the LFO.  One transistor, three 1uF caps, three resistors and a pot will get you what you need.

[Bob33]

Try the EA Trem LFO.
http://www.runoffgroove.com/eatremolo.html

The rightmost part of the schem is the LFO.  One transistor, three 1uF caps, three resistors and a pot will get you what you need.

Amazing! THank you so much!!  I'll try it out as soon as I get some extra allowance for parts!!!

You totally made my day Travis. Thanks a bunch!

[gez]

Like this... this looks perfect, but to adjust the rate requires adjusting the value of two resistors and a cap, but I just need a simple pot to adjust those things... hrm....



http://www.kpsec.freeuk.com/projects/flashl.htm

I see a lot of them 555 chips in various blinking diagrams.. but once again.. no rate control via  pot...

This is the stock way to wire a 555.  They're better if you connect them up as you would a CMOS Schmidtt Trigger oscillator circuit rather than as shown.  Get rid of R1 and connect R2 between pins 6&2 and the output (pin 3).  This leaves the discharge transistor to drive the LED - connect LED and series resistor R3 from V+ to pin 7.

As well as avoiding loading on the output you get a 50:50 duty cycle.  Just include a pot in series with R2 to make the rate variable.

f = 1/(1.4XRXC)

Use a CMOS timer (7555) to avoid excessive battery drain.

PS That astable circuit shown will suck a battery dry pretty soon with only 330R resistors (nearly 20mA thru each LED).  If you use low current LEDs/super brights you can get away with just 2mA.

[AL]

Try the Lights and Light Controlling link at the bottom left.

http://www.epanorama.net/index.php

AL

[petemoore]

I've got a 555 blinker here with a 100k pot for speed control.
 To further extend the speed control [the high setting something like 6X faster than the low setting] I socketted the electrolytic cap and by changeing it's value, I can get the blinker to go very fast or extremely slow...

[R.G.]

The devil makes me do this...

No problem. Use a 12C508 PIC ($1.25), a 10K pot and a 0.1uF capacitor, with a current limiting resistor from one of the output pins to the LED.

Program the PIC to read the value of the pot, then blink the LED at one of 256 rates that the pot value selects.

You get to pick (no pun intended) whatever range of rates you like; they don't have to be linear or even monotonic.

It's a simple matter of programming...

[mattv]

The devil makes me do this...

No problem. Use a 12C508 PIC ($1.25), a 10K pot and a 0.1uF capacitor, with a current limiting resistor from one of the output pins to the LED.

Program the PIC to read the value of the pot, then blink the LED at one of 256 rates that the pot value selects.

You get to pick (no pun intended) whatever range of rates you like; they don't have to be linear or even monotonic.

It's a simple matter of programming...

I've seen some diy programmers and free-ware programs online,  but is there any one in particular that you'd recommend? PICs seem really interesting and versatile, but it may take some easing into.

[niftydog]

diy programmers and free-ware programs online

diy programmers can be cheap and useful.. Just be sure to get one that is compatible with your PIC.  In Circuit Serial Programming on some PICs makes it even easier to do... need to do some research cause I ain't got time to explain it all to you!

...best thing would be to go to //www.microchip.com and download MPLAB IDE.  This has the assembly programmer, a compiler and a simulator that I've found incredibly useful.

There's also heaps of data sheets and other pdfs at this site that will help you ease into PICs.

Might also be an idea to seek out a "for dummies..." type book on the subject.

[Gilles C]

>>>The devil makes me do this...

No problem. Use a 12C508 PIC ($1.25), a 10K pot and a 0.1uF capacitor, with a current limiting resistor from one of the output pins to the LED. <<<

YES,YES,YES... :twisted: