• Some users have recently had their accounts hijacked. It seems that the now defunct EVGA forums might have compromised your password there and seems many are using the same PW here. We would suggest you UPDATE YOUR PASSWORD and TURN ON 2FA for your account here to further secure it. None of the compromised accounts had 2FA turned on.
    Once you have enabled 2FA, your account will be updated soon to show a badge, letting other members know that you use 2FA to protect your account. This should be beneficial for everyone that uses FSFT.

Pulsing LEDs question

A

andypnb

Gawd
Joined
Dec 18, 2002
Messages
964
Hey all,

I am trying to make a mod thing and I though I would ask my questions here, where the experts can provide some advice.

This is what I am looking for:
I want a string of some 20-30 LEDs, to pulse from On to Off, slowly, and all of it run on batteries.

I have found this:
http://www.rabidhardware.net/?id=5

And thats essentially what I am looking for on a small scale. I need at least 20 LEDs , so much higher drainage, and I guess I can use a 9v battery or two as in that example. I can also use AA or AAA, as space permits it just fine.

Any advice on how I can accomplish this? Will 20-30 LEDs drain a 9v battery very quickly? A couple of them? Can I just do what that page does and simply put the LEDs in parallel?
 
Take a look at the schematic, and find R7--it's the one attached to the LED. See how R7 and the LED are in series? What you need to do is to make 20-30 of those LED-resistor strings, and connect them all in parallel with the original R7 and LED.

Keep in mind, though, that with 20-30 LEDs, you'll be pulling 400-600mA. That's not a huge amount of current, but it'll drain your 9V in well under an hour. For this kind of application, you probably want to get either a heftier battery pack or an AC/DC adapter.
 
Mohonri said:
Take a look at the schematic, and find R7--it's the one attached to the LED. See how R7 and the LED are in series? What you need to do is to make 20-30 of those LED-resistor strings, and connect them all in parallel with the original R7 and LED.

Keep in mind, though, that with 20-30 LEDs, you'll be pulling 400-600mA. That's not a huge amount of current, but it'll drain your 9V in well under an hour. For this kind of application, you probably want to get either a heftier battery pack or an AC/DC adapter.
Click to expand...

I really only need it for about an hour at a time before I change the battery pack. Plus if I get 2 9v batteries, then I should have about a 2 hour window (duracell batteries say about 500mAh).
Also, since I am running 9v I would remove the first resistor R6 correct?
 
To be honest, I don't know why R6 is there in the first place. You *should* be fine without it, no matter what the supply voltage. The LM 1458 can handle supply voltages up to +/-18V, so the 9V shouldn't be a problem at all. Using two 9V batteries in parallel will more than double your run time. The less you drive a battery, the more total capacity you get.
 
You must log in or register to reply here.
Back
Top