I'am developing a simple badge with a fading led. My idea was a LMC555 timer powered by a cr1025 battery, these batteries have a nominal voltage of 3v. I chose the LMC555 for its low operating voltage. https://www.ti.com/lit/ds/symlink/lmc555.pdf
I have ordered my parts and made the circuit following this instructable: https://www.instructables.com/id/LED-fading-with-a-555-timer/ and this schematic.
I used these parts:
- LMC555 timer
- 220uf electrolytic capacitor
- 2N2222 npn transistor
- two 1206 red LED's 1.7V forward voltage
- 1.5k resistor instead of 20k for better timing
Powered by a my lab bench powersupply set to 3V. The circuit starts only working above 4.5V, I tried changing the current limiting resistor to a higher and lower value and changing the npn transistor for a ao3402 mosfet http://aosmd.com/res/data_sheets/ao3402.pdf , but that did not help. I even tried removing the current limiting resistor so that there is no voltage drop over the resistor.
Because the fading is to fast to be measured with my multimeter and my oscilloscope stopt working last month I tried to simulate the circuit in LTspice. Here you can see the LMC555 is giving the full 3V on the output, but on the end the led gets only 700mV. What did I do wrong, is it even possible? I hope somebody can help me solving this problem.