I am placing a micro fan inside my Samsung AstroVideo camera and it is a 5 volt fan.
I have 12 volt running into the camera (the camera's own power supply).
Today I went to Jaycar and bought a voltage regulator for the fan (7805).
My question is, can I wire it directly or do I really have to use capacitors each side of the Regulator?
I am placing a micro fan inside my Samsung AstroVideo camera and it is a 5 volt fan.
I have 12 volt running into the camera (the camera's own power supply).
Today I went to Jaycar and bought a voltage regulator for the fan (7805).
My question is, can I wire it directly or do I really have to use capacitors each side of the Regulator?
Here is what I mean:
Unfortunatly yes you need the caps.. The regulator won't work correctly without them..
Strictly speaking, according to the NatSemi datasheet, neither capacitor is required
for the regulator to operate. However, the datasheet recommends a 0.22uF on the
input "if the regulator is located far from the power supply filter", which in your case,
is unlikely and "although no output capacitor is needed for stability" one "does
help transient response" and they recommend a 0.1uF ceramic capacitor.
See http://www.national.com/ds/LM/LM340.pdf
You will certainly have to be careful with any noise from the fan and in any case,
always using capacitors represents good practice. Use a 0.22uF tag tantalum of appropriate
voltage rating (e.g. 35V) and low ESR on the input. Use a ceramic 0.1uF bypass cap on the output.
Strictly speaking, according to the NatSemi datasheet, neither capacitor is required
for the regulator to operate. However, the datasheet recommends a 0.22uF on the
input "if the regulator is located far from the power supply filter", which in your case,
is unlikely and "although no output capacitor is needed for stability" one "does
help transient response" and they recommend a 0.1uF ceramic capacitor.
See http://www.national.com/ds/LM/LM340.pdf
You will certainly have to be careful with any noise from the fan and in any case,
always using capacitors represents good practice. Use a 0.22uF tag tantalum of appropriate
voltage rating and low ESR on the input.
Thanks Gary.
All I have is two 470uf and a few 1000uf Electrolytic Capacitors I can get out of an old dead PC I have.
I don't have any Ceramic ones (the 0.1uf & 0.22uf ones).
Quote:
Originally Posted by gary
You will certainly have to be careful with any noise from the fan
The fan is going into the camera to blow cold air onto the front PCB to help reduce noise. I hope I don't introduce more.
All I have is two 470uf and a few 1000uf Electrolytic Capacitors I can get out of an old dead PC I have.
I don't have any Ceramic ones (the 0.1uf & 0.22uf ones).
If you were planning on using the camera over the weekend, you can dispense with
the capacitors for now. When you get a chance, order a 0.22uF or 0.33uF tantalum
of a rating of, say, 35V for the input and a ceramic disk 0.1uF (100nF) for the output.
Solder them straight across the input terminal to ground and the
output terminal to ground, as in your original drawing, and keep the leads short.
I am putting a peltier cooler on the outside of the camera body to cool down the whole body so I don't cause cold shock to the chip.
The fan just blows the cold air inside the case towards the front where the chip is.
I have tested it with a 12 volt fan and it got rid of 99% of the noise.
But the 12 volt fan doesn't quite fit in there properly, that's why I am using the little micro fan.
Don't forget that the regulator will disipate more heat that the wattage of the fan because it is absorbing more than half the power from your supply. Put it on a heat sink.
As Gary says. The regulator does not actually need the capacitors to work but HF noise on the lines can be reduced by proper by-passing on the input and output. Those high capacity electrolytic capacitors are not particularly effective against HF noise. A .01ufd ceramic will be better for this.
Hi, the capacitors used in power supplies are related to the amount of power produced. More power the higher the capacitance needed values you have should be fine. The Voltage rating should be approx 16V on the input and 6.3V on the output. 6.3V on the input won't last long without an explosion and loads of oily paper splatted all over the inside.
I have just done some reading up about it and yes, the regulator will get quite hot needing a heatsink, but I don't have room to add that too, so I will first attempt to track down a 12v micro fan.
I have seen them online at 30mm x 30mm x 6mm.
Even a 35mm x 35mm will just fit, so I have two options in 12v.
The one I have now is 40mm x 40mm and it just won't quite squeeze in.
If I have no luck I will return to this 5v fan and have to add a heat sink somewhere.
Well, this is a regulator, albiet $16 odd, that doent need a heatsink, uses half the power and has exactly the same layout/circut as the 7805 you have.
No biggy, whatever you find cheaper ;-). If you find you need to use a 5v fan, this regulator is a lot easier to use, and takes less space than a 7805 with a heatsink.
Bad luck about the fan. I just threw a bag full of them in the garbage. They were second hand but in good condition. I bought them about 4 years ago to cool the regulator in some small power supplies that I had to repair.
Well, this is a regulator, albiet $16 odd, that doent need a heatsink, uses half the power and has exactly the same layout/circut as the 7805 you have.
No biggy, whatever you find cheaper ;-). If you find you need to use a 5v fan, this regulator is a lot easier to use, and takes less space than a 7805 with a heatsink.
Thanks Fred. It might be worth me looking into
Quote:
Originally Posted by Barrykgerdes
Bad luck about the fan. I just threw a bag full of them in the garbage. They were second hand but in good condition. I bought them about 4 years ago to cool the regulator in some small power supplies that I had to repair.
i dont know why opened this thread im not an electric guru 
i just wanted to see what your up too 
Murphy at it again
