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What are the alternatives of LED Flasher/Oscillator LM3909?

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Johnson777717

New Member
The best alternative that I know of would be a 555 timer. It's basically the same thing, and in my opionion, more versatile. These IC's are very cheap, and available at Radio Shack, as well as any electronic supplier. If they don't have 555 timers, then there's something wrong. Check the pin outs for the 555 timer versus the 3909.

Check here for a pretty brief 555 timer tutorial:
https://www.meridianelectronics.ca/gadgets/555/555.html

Pretty much every major non-specialized semiconductor manufacturer has a 555 timer that they make. National Semiconductor = LM555. NTE = NTE955M etc.
 

k7elp60

Active Member
LM3909 replacement

The easiest replacement for the LM3909 is a standard flashing LED, although you cannot set the flash rate.
 

bogdanfirst

New Member
LM3909 is not intereting...
for a 1.5V flasher use a COMOS 555 like ZSCT1555(works down to 0.9V).
also try LMC555, TLC555 ICM7555
 

duffman

Member
I found a 555 oscillator replacement for the lm 3909 in the Trackign transmitter but it uses a 6 volt power supply.

The components are a 10 uf electric cap
a .01 uf ceramic cap
a 22 resister
a 10k resiter
and a 330 resister.

HOw do I convert these to 1.5 volts?
 

duffman

Member
fascinating!! so a 555 timer circuit at 6 volts, uses the same components at 3 volt?! thats awesome. But doesnt the rate of flashing and all that rely partially on voltage?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
duffman said:
fascinating!! so a 555 timer circuit at 6 volts, uses the same components at 3 volt?! thats awesome. But doesnt the rate of flashing and all that rely partially on voltage?

It's fairly independent of supply voltage, basically because it charges a capacitor to a percentage of the supply, not to a specific voltage.
 

Roff

Well-Known Member
bogdanfirst said:
LM3909 is not intereting...
for a 1.5V flasher use a COMOS 555 like ZSCT1555(works down to 0.9V).
also try LMC555, TLC555 ICM7555
The problem is overcoming the LED forward voltage drop while using a 1.5v (or less) supply.
 

k7elp60

Active Member
Here is a circuit that uses a 74AC14. I downloaded it sometime ago
from the internet.

Please ignore my post, I could not get the schematic to upload.
 

duffman

Member
Ok. Well, this is all related to building the tracking transmitter I'm assuming. THis is what started it all anyways.

It seems to me that all the 3909 did was provide an oscillating signal, that would be put through the coil. Wouldn't a blinking LED do the same thing? Granted it would need 3 volts, which would bring me to our next question. What would running the transmitter circuit at 3 volts do. Wouild it change the frequency? WOuld it make the signal stronger? Also I have a question about inducting signals with coils. This seems like a very crude way to do it. Using wire and all. However, does the wire affect the signal produced. I am using braided wire instead of solid wire and I was wondering if that was affecting anything.

Also, in different posts, people have talked about how they tried to breadboard RF circuits and came up with unsatisfactory results because of built in capacitance from the breadboard. would this also apply to the tracking transmitter circuit?
 

Hero999

Banned
No problem, the 555 can act as a voltage doubler.
 

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mneary

New Member
alanzhao said:
Does anyone have LED flasher circuit diagram using 1.5-3v battery and 555 timer?
I found this in a quick search.... four transistors and a few resistors.

[edit] I just noticed that the OP hasn't posted anything since Feb. 2004. :eek: [/edit]
 
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