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Topic: atmega328 glitching on and off (Read 1 time) previous topic - next topic

Joes

hi there i have made a control board for a heating system that i work with on a regular basis was in the process of fine tuning my code to work correctly so all hardware seemed to be working ok but just recently it seems like the processor is switching on and off continously. hardware:
8va transformer 24v output
KBP005M rectifier
16uf capacitor changed for 33 and then 1000 still no different
L7805 Voltage Regulator  was changed no different
16uf capacitor changed for 33 and then 1000 still no different
atmega328 works fine in the arduino board and has been replaced aswell
the 2 capacitors and crystal have been changed still no difference

when i changed the two capacitors either side of the voltage regulator to 1000uf when you turn the board off it suddenly seems to work for a split second just before the capacitors discharge 

any ideas?

Joes

just had another play and just ran two temporary leads picking up the pos and neg from te board and linking them to the 5v out on the arduino programming board it appears to work fine then bit hard to exactly say as some of the componenets will not work as they need higher voltages so i presume my bridge rectfier needs replacing or the voltage regulators im using are a load of crap?? but seem to test out ok on the multimeter

Nick Gammon

The meter won't show everything. An oscilloscope might.

Try some decoupling capacitors.

http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

oric_dan

Quote
some of the componenets will not work as they need higher voltages


If the 328 works with a separate 5V on it, but not when running off the 7805,
then it sounds like some of the other components in the circuit may be crowbarring
the 7805.

buteman

Just a thought about voltages in your circuit.
Your transformer will give a peak voltage of 1.414 x 24 volts ( 33.936 ) at the rated output. If you are drawing less current, which seems likely, the peak voltage will be higher. The spec for a 7805 is maximum input 35 volts, your rectifier will drop a few volts but it might still output more than 35 volts so it might keep shutting down.

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