Here is a handy little project I designed and built. It's a spin off of the classic LM555 CW Oscillator. But wait N1IR!.....isn't that a AA battery in the circuit? Why yes! the LM555 minimum voltage is 4.5 Volts so I design this circuit with a TLC551 LinCMOS, this is a direct replacement of the LM555 but can operate as low as 1 Volt! I chose this IC because the AA battery is less expensive and will last longer than a 9V and smaller foot print.
What's with pin 3 connected directly to the base of the TLC551? I thought you needed current limitation of the transistors? Yes and no.....with the supply voltage so low and current limitation of the IC (1mA) you can get away with it, thus reducing parts count.....but if you want a higher voltage let's say 3 volts or more you will need a current limit resistor from pin3 to the base's.
How do I change the battery? Well this is a prototype that was originally designed for one use disposal for a CW training class, the battery life is past 200 hours continuous use at 50% duty, far exceeding the class time. If you would like an easier battery replacement Radio Shack sells a AA battery holder you can solder in place of the current battery. Full production model may have a battery holder pending price.
What connector is that connected to your key? I used a SIP connector I salvaged off a computer case, this again was to make this as inexpensive as I could.
How about a BOM?
Will you sell me one for $5.74? NO!.....how about $10.00? NO!....How about $20.......NO! If you would like one please sign up for our upcoming CW class course at the Genesis Amateur Radio Club, they are a donation for students for our class only.