4 ms·
What component values do you need to time exactly 55 years? Maybe it could work if you used 5 timers?
by amelius 6mo ago
What component values do you need to time exactly 55 years?
Maybe it could work if you used 5 timers?
- megous 6mo agoI don't think you could do it. Not with the original BJT variant anyway. :)
- floxy 6mo agoHmm, why not? For the astable configuration, you could use a 100F capacitor with R1 = 10 Meg and R2 = 7.5 Meg, for a 55 year period. Base current for the Threshold NPN will come from the Trigger PNP (and hopefully temperature drift matches OK). Other than maybe the 100F capacitor might have some variation in capacitance and leakage current over the course of 55 years ;-) https://www.digikey.com/en/products/detail/tecate-group/PBLH-12R0-100ST/12323423?s=N4IgjCBcpgnAHLKoDGUBmBDANgZwKYA0IA9lANogAMIAugL7EBMVALEtCGpFnkaRRDwqAAgBiIYmCqiJtYgAcALlBABVAHYBLJQHl0AWXyZcAVwBO%2BEIxAsA7B1QYcBYmUiUwTEQDU6ilUh1bT1DYzNLa2IAWiZkLiglc1N%2Bd0oAVjp6bKA https://www.digikey.com/en/products/detail/tecate-group/PBLH...
- speff 6mo agoOnce you get above a couple meg, the oils on your fingers start affecting the resistance. Better hope no-one touches with your 55 year counter
- megous 6mo agoat 1% initial precision of just eg. LM555 itself, you're looking at +-0.5 year just from the chip's contribution. If you ever find 100F 1% precision capacitor and 0% precision resistors, you may maybe hit +- 1 year if the other conditions are perfectly predictable, which they are not. For your chosen capacitor, manufacturer doesn't even bother providing the tolerances. :) Good luck with that.
- ua709 6mo agoHow exactly is exactly? Can I make it measure 1 hour with an allowed tolerance of 55 years, plus or minus. :)