0
\$\begingroup\$

I have bought 6 of the 20-string LEDs for a hobby project of mine. http://www.amazon.com/Warm-White-Lights-Silver-Wire/dp/B004E328A4/ref=pd_sim_hg_9

I wish to make them blink at a fixed frequency anywhere between 10Hz and 20Hz. I wish to use only one or two battery packs (3 to 6 AA batteries total) to power all 6 strings (the final circuit needs to be compact).

A single string of LEDs draws 120 mA of current. Fresh AA batteries supply 1.5 Volts each. So, each string should draw 3 * 1.5V * 0.12A = approx 0.5W per LED string.

I am looking for an LEd driver that will make the LEDs blink. My estimates is that I need 4 +/- 0.5 V, 1.5W or 3W +/- 20% for both, 15 +/-5 HZ LED driver.

I have tried a few searches and did not find anything that seems appropriate, probably because I am a beginner.

Please suggest a component. It should draw the same power as it modulates I assume it should not be bigger than a US quarter coin. Hopefully I have done my arithmetics right.

UPDATE:

I ended up using the 555 / astable circuit like this one: http://www.555-timer-circuits.com/flashing-led.html Here is a calculator I used: http://www.ohmslawcalculator.com/555_astable.php

So far so good.

\$\endgroup\$
1
\$\begingroup\$

I would use a LM555; it's a very flexible, cheap, and easy-to-find timer chip. And you can find lots of examples on how to use it. Here's one to start with. The 555 will source around 125mA, which isn't quite enough for your application. If want to drive all of the strings at once, you can do it with an NPN transitor switch hooked to the output of the 555. I would probably start with a TIP120; that's hefty enough to handle the current you need to switch. You will need a way to power all of the strings at once. If you are using batteries, I would use 3 D cells to drive all of the strings. If you are okay with a plug-in solution, you can find lots of small wall wart power supplies that put out 5V at 1Amp; they are used to charge cell phones and other kinds of electronigs

\$\endgroup\$
  • \$\begingroup\$ Thank you! 555 is great. I am using the "astable" flavor and I got a single LED to blink. I will end up using a transistor to amplify the power of the resulting rectangular wave. \$\endgroup\$ – Job Jul 26 '13 at 23:19

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.