I have a lot of components and wires on a prototyping board, one component being the DS1307 real time lcock. Anyway, I have a problem with the components: when using the PWM function with an LED the DS1307 becomes unstable.
I believe I can fix this if I make the power/data lines going to it more stable, and have little experience with but have heard about filter capacitors.
How would I use a filter capacitor? What value should it be? What lines should I place the capacitor(s) between?
Do you have 0.1uf caps on all Vcc+ terminals of your chips/avr connected to ground? Place 0.1uf cap near pins as much as possible.
May also help adding a small, say 47uf to 100uf caps across your power terminals, Vcc to Gnd.
I agree with vasquo adding the caps near the Vcc terminals on the DS1307 will help reduce the noise that the PWM can cause
The power supply is a +5V regulator and there are 2 electrolytic capacitors, a 100uF cap between the unregulated voltage and ground, and a 10uF cap between the regulated +5V and ground.
I will have to try the 0.1uF caps though, thanks! I'll check it out and post the results.
You need to read the datasheet about the DS1307 and the need to keep the 32768Hz crystal away from any other signals and near
a ground plane - they show suggested layout details needed to keep the oscillator stable (the RTC clock oscillator uses
a fraction of a microamp only, its very high impedance and sensitive to interference.)