Greetings
The LM3909 was an adjustable rate flasher; now it is a ripoff.
Is there a modern chip or an useable portion of a chip guts that does the same, 30+ years later ?
Adjustable duty, 1.5V ? There is several clever circuits published on the web to perform similar. Any that you prefer ? No 555s, please.

 

They are a $1.00 at newark?

 

Schmitt trigger oscillator



UJT oscillator

 

Joule thief circuit

 

NPN-PNP transistor oscillator

 

I think a joule thief is your best bet.

Didn't realize LM3909 had gotten so expensive. I got half a dozen free NTE parts at a swap meet 4-5 months ago. Plus, I have stock from the 70's...

 

They are a $1.00 at newark?

Nope. LM3909s are quite extinct. You won't find them at Newark or any of the regular suppliers. According to Octopart, there is one source for them, where you will pay dearly.

 

mouser.com claims they can special order from TI.

 

Even the cheapest ones on AliX... And not much better priced in small lots. Note the only 92% Positive Feedback for the vendor.

 

I'd only buy commodity semiconductors on Ali Express. They're less likely to be counterfeit.

This photo gives enough detail to tell it's counterfeit:

Note the debris in the pin 1 mark and the pitting (non-shiny) nature of the pins.

 

Nope. LM3909s are quite extinct. You won't find them at Newark or any of the regular suppliers. According to Octopart, there is one source for them, where you will pay dearly.

8 pin Microchip for $1.00
Customizable!

 

Yes, I would avoid them also for this. Just for comparison and the price has been relatively high for years which is why my blinkies either used a uP or 555. One possibility that Mr. Chips didn't mention is using an ATTiny chip and programming it to blink. The Arduino IDE even comes with a standard 1s blink example program. The ATTiny85 is significantly cheaper then the LM3909 albeit more than the 555.

 

my blinkies either used a uP or 555.

LM3909's claim to fame is that it has low battery drain and gives good brightness from 1.5V with low parts count.

 

Yup, they built, I'm sure, millions of battery powered construction barrier blinkers with them.

 

Yes, I would avoid them also for this. Just for comparison and the price has been relatively high for years which is why my blinkies either used a uP or 555. One possibility that Mr. Chips didn't mention is using an ATTiny chip and programming it to blink. The Arduino IDE even comes with a standard 1s blink example program. The ATTiny85 is significantly cheaper then the LM3909 albeit more than the 555.

However, you do have to buy an ATTiny programmer. It’s $15-$20 on Sparkfun. But it’s a one time purchase and can be amortized over many projects.

In case it’s not obvious, you can use the Arduino IDE to program and upload code to the ATTiny.

 

In the world of IC oscillator designs, the 3909 was unique. The reason it got such a relatively long battery life is that it used the charge built up in the capacitor (as part of the timing circuit) to power the LED. I always like this getting double duty out of those electrons, and have "borrowed{" the idea a few times.

ak

 

With all the brains of this site together; is there a way to re-purpose a YX8018 chip (used in 1.25V solar garden lights) to make it flash ?



-The solar panel could be ignored-

 

Yes, use a flashing LED.

 

Below is the LTspice simulation of a two transistor circuit, similar to Mr Chips' circuit, that adds the capacitor discharge voltage to the battery voltage to drive LED from a 1.5V battery (similar to the LM3909).
It oscillates at a 1s period with about a 6ms pulse to 1/2 amplitude with about a 60mA peak amplitude.
The average current draw from the battery is about 1mA.
The simulation works down to a 1V battery voltage.