Hourglass Soldering Kit with IC 4015 and IC 4069 (2/2)

[@fphenix]

Good video. I am waiting to receive the kit. I have a question though: How could the current limiting resistors be 3300 ohms? With a blue led (for instance, as that is the kit I ordered), Vf is about 3.1V, so under 5V that'll be a current less than a milliamp (about 0.6mA). A classic 5mm Led usually needs between 5 and 20mA (Low current ones need 2mA). How do those Leds even light up?!

[@patrickgaerdelen]

I build the kit but when turning power on , leds go on but do not change...looks like clock circuit is not running ....where do i CHECK ?

[@fphenix]

Without a scope it'll be difficult to pin point the issue. I'd check there are no short around the tilt-switch and around the oscillator (i.e. the 4069 IC, R31, R32, C1 and VR1). I would also check that the R31 (1Meg) and R32 (3k3) resistors are not swapped. The pity is that the oscillator they use is based on 2 inverters, which is known to not oscillate under certain conditions, unlike the 3-inverters oscillator that will always oscillate (and there are 4 unused inverters in the 4069 chip, so whoever designed this kit could have used one more very easily...). Note: I don't have the kit yet.