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wonder if I need better power supply?

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MrDEB

Well-Known Member
Finally going to build this circuit but really wondering just how good are the RS wal warts?
Thinking maybe adding a diode in series to pin 14?
maybe a 5v zener??
or just don't worry about it?
 

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JimB

Super Moderator
Most Helpful Member
I am not sure about "RS", do you mean "Radio Shack" or the UK company "RS Components".
If its RS Componenets, no problem, if Radio Shack, no idea.

Looking at your circuit, there are a few wrinkles and errors, I have had a go at editing it to remove what seems wrong to me.

JimB
 

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MrDEB

Well-Known Member
oups I guess when I rotated etc the programing port (supposed to be a 5 pin plug) I got the labels switched around.
RS in the states is Radio Shack. Not sure of how well regulated the wal wart is.
Maybe just insert two diodes and ake a 1/2 wave rectifier?
 

MrDEB

Well-Known Member
maYBE OVERKILL OR JUST BEING SAFE?

The power supply kinda has me concerned.
Have a 4.5v Radio Shack wall wart.
woried about how well regulated without going over 5v.
output is two sets of 3 LEDs
see schematic pins 8, 9, 17
each pin drives two LEDs in series
current draw is very min. being the pic is using PWM to drive the LEDs.
R5 is to adjust LED brightness.
 

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3v0

Coop Build Coordinator
Forum Supporter
I buy wall warts at the local thrift store for $1 or less. I do not trust the regulation. They are often over voltage or maybe the voltage depends on the load.

I build little PCBs with a regulator, the required 2 caps and a power indicator LED on the regulated side. The PCB has a 2x3 male header that plugs into the power strip of a solderless BB. The wall wart connects to screw terminals. I etch several of the little regulator PCBs at a time and populate them using a regulator with the voltage and current I need for each project.

The current version is for TO-92 package regulators which limits it to 300mA. I like it so well that I plan to make similar ones for larger regulators.
 

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be80be

Well-Known Member
I buy wall warts at the local thrift store for $1 or less. I do not trust the regulation. They are often over voltage or maybe the voltage depends on the load.

I build little PCBs with a regulator, the required 2 caps and a power indicator LED on the regulated side. The PCB has a 2x3 male header that plugs into the power strip of a solderless BB. The wall wart connects to screw terminals. I etch several of the little regulator PCBs at a time and populate them using a regulator with the voltage and current I need for each project.

The current version is for TO-92 package regulators which limits it to 300mA. I like it so well that I plan to make similar ones for larger regulators.

That's the best way to go $1.00 wall wart and $1.00 for parts and your good to go
 

MrDEB

Well-Known Member
As the black smoke rises from the pc board --lol
I already have a wall wart and not really wanting to buy aditional.
I even contemplated just a simple zener diode to control most over voltage?
 

MrDEB

Well-Known Member
this looks promising

just hope local rat shack has a 4.7 zener and a 10 ohm resistor(or close)
very basic. better than nothing at all.
 

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MrDEB

Well-Known Member
No zeners at Radio Shack

next option = I have some LDO regulators. Im pretty sure an LM2937 5v units.
Probally won't work with 4.5 dc input.
any other suggestions?
 

gabeNC

Member
I do something similar to 3vo. I have an old playstation1 power supply, DC 7V 2amp and I run that through a 7805 with a diode for reverse polarity protection and required decoupling caps. Plus I threw a led in there for status. Watching the input with the dmm and the regulation out of the power supply does float around quite a bit.
 

MrDEB

Well-Known Member
thats my last option, connecting a 9 or 12v voltage source.
I have a 4.5 in hand but need to locate a 9 or 12. pretty sure I have somewhere.
still like the zener idea
 

gabeNC

Member
One thing I like about this PS, is that it's only 7V... I had used a 12V before and I needed a heatsink on the 7805.
 

DirtyLude

Well-Known Member
Oh! Oh! I made some of these as well.

Unfortunately my LDO footprint was off, therefor the green wire (actually blue) correction. Mine also have the option to take power from a USB connection, since I tend to do work on my laptop. It does not have RP protection, though, which I should add.
 

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MrDEB

Well-Known Member
Well my brother went to the big city today and visited a Radio Shack.
only zener found ad bought was a 5.1
I guess using the 5.1 followed with a 1n4148 should keep the voltage below 5v??
input is a 4.5 wal wart from Radio Shack.
better than no insurance of regulation or buying a different wall wart transformer??

any thoughts on this idea?
 

be80be

Well-Known Member
what more would you want
Power your device that requires 4.5VDC and up to 700mA. You can customize your power with the correct Adaptaplug™ (sold separately). Good as a backup or replacement power source for your device, a noise filter is included to reduce noise from the adapter. UL listed and ENERGY STAR® compliant.

* Delivers 4.5VDC and up to 700mAh to your device
* Just select the appropriate tip for your device (sold separately)
* Replaces catalog #2731765
 

MrDEB

Well-Known Member
I don't want to purchase another wall wart.
contemplating just gong with the wal wart 4.5vdc and hopfully it will not destroy the pic.
oh yea I found out that the location where the tabernacle that the pic is to be installed in is "off grid". hopfully somewhat clean power?
 

MrDEB

Well-Known Member
ordered some wall warts from Goldmine yesterday. No voltages listed or ?
Waiting for shipment then decide on either the LM2937 5v or a 7805.
the 7805 is overkill perhaps and seeing I need very little power-a pic, 6 LEDs using PWM and a photo transistor.
 
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