Blazemaguire
Senior Member
Hi,
I'm running a 20m2 circuit with a 12V 5A DC power brick. (the 12V is powering a stepper motor through a L298n driver)
I'm intending on using a 7805 to drop to 5V necessary for the PICAXE. Where should I fit the standard (ish) 104 ceramic and 100uF electrolytic decoupling capacitors? (I'm good with bolting circuits together, but this side of things is beyond my level of understanding).
Do they go between 12V and 0V (as close as possible to the source) or do they go after the voltage regulator? (i.e, between Ref(which goes to zero volts anyway) and the regulated 5V output? or... do they go in both places? As I don't really know the theory for why they are necessary, I don't really understand where to place them either!
I've had my rig successfully working on a breadboard on the bench, but running from a PC power supply that supplies 5V and 12V on different rails (also, with some decent noise prevention included I'd imagine?) I just put the caps on the 5V rail on my breadboard for now, but as it worked with and without them, I don't know if that's correct!
I'm in the process of transferring to a PCB design now, which will be using a different PSU and onboard regulation to 5V.
Also, if anyone has any other recommendations for making this kind of circuit reliable let me know. It's a one off project for somebody and I would like it to be as reliable long term as it appears to be on my bench setup at the moment. - to Clarify, I'm not experiencing any issues with noise / PIC resetting / as yet. But I'm wondering if the PC powersupply is somehow shielding me from a poor circuit design.
I've read the 7805 is not very efficient as far as regulators go, but efficiency is not important as it's not a battery powered device. The regulated only has to supply a PICAXE, a few LEDs and an MP3 sound module board so shouldn't be drawing anyway near its 1A limit.
I'm running a 20m2 circuit with a 12V 5A DC power brick. (the 12V is powering a stepper motor through a L298n driver)
I'm intending on using a 7805 to drop to 5V necessary for the PICAXE. Where should I fit the standard (ish) 104 ceramic and 100uF electrolytic decoupling capacitors? (I'm good with bolting circuits together, but this side of things is beyond my level of understanding).
Do they go between 12V and 0V (as close as possible to the source) or do they go after the voltage regulator? (i.e, between Ref(which goes to zero volts anyway) and the regulated 5V output? or... do they go in both places? As I don't really know the theory for why they are necessary, I don't really understand where to place them either!
I've had my rig successfully working on a breadboard on the bench, but running from a PC power supply that supplies 5V and 12V on different rails (also, with some decent noise prevention included I'd imagine?) I just put the caps on the 5V rail on my breadboard for now, but as it worked with and without them, I don't know if that's correct!
I'm in the process of transferring to a PCB design now, which will be using a different PSU and onboard regulation to 5V.
Also, if anyone has any other recommendations for making this kind of circuit reliable let me know. It's a one off project for somebody and I would like it to be as reliable long term as it appears to be on my bench setup at the moment. - to Clarify, I'm not experiencing any issues with noise / PIC resetting / as yet. But I'm wondering if the PC powersupply is somehow shielding me from a poor circuit design.
I've read the 7805 is not very efficient as far as regulators go, but efficiency is not important as it's not a battery powered device. The regulated only has to supply a PICAXE, a few LEDs and an MP3 sound module board so shouldn't be drawing anyway near its 1A limit.