Per-Anders MLD-01 to power cooling fans??

[spence]

Hello All!

I was looking for a way to power a few cooling fans at 6 V or so, and ran across this project from Per-Anders:

http://home.swipnet.se/~w-50719/hifi/mld01/index.html

My questions are:

1. Can I use this with 120V mains to run cooling fans (of course component values should be changed to allow the correct voltage and current based on the equations provided on the page)?

2. Any drawbacks to doing it this way???


Opinions please!!

Thanks in advance, Spence

[lineup]

hi

I would not do this.
Even if I could.

If only a few mA to power a LED lightning diode.
Yes, maybe. But I wouldn't like to do it anyway ......

To drive any other circuit that takes more power, NO!!!!
To drive even a very small FAN at 6 volt, you need more Current than a few milliampere.

Use a little 6 or 9 Volt AC transformer. With a little 1-2 ampere rectifier bridge.
You could regulate to get exact 6 Volt DC, by using 7806 3 pin regulator.
(Or using LM7805 + 1-2 diodes to raise 5.0V get ~ 6 volt output.)

I am sure peranders will agree to this is much better.
================================================

from peranders website

MLD-01 The Mains LED driver

WARNING - CAUTION

As you can see at the picture the pcb will be at mains potential and therefore lethal. You must ensure that this pcb is well protected against unintentional touching. All parts are dangerous to touch when the mains is switched on.

and

The power for the electronics is derived through a capacitor which acts like a "lossless resistor". This technique is possible to use if the wave shape of the mains is good enough (sinus with no harmonics). The size of the C1 and C2 is rather critical. If you are going to use 110-120 VAC the capacitance must be double, but this isn't tested yet, the exact value.

For this application you can rather easily calculate how big C1 and C2 should be on order to get desired brightness of LED. The calulation below will get you the total current.

I = Umains*2*3.14*f*C

C = I/(Umains*2*3.14*f*) = 10E-3/(230*2*3.14*50)=138.5 nF for 10 mA current.

f=50 or 60 Hz

Since the incoming voltage is 230 V and the voltage you want is very low, like 5-10 volts you can consider the caps as a current generator. It means that you will get the same current regardless of load.. and... you must not break the circuit!

Small 3 pins voltage regulators, TO220 package, Max 1A = 1000mA
http://www.fairchildsemi.com/ds/LM/LM7806.pdf

See my attachment, for typical simple regulator circuits.
Best to put LM7806 regulator at a piece of aluminium,
at least for current above 0.1-0.2 Ampere and when is more than a few voltage drops
from input to output.
( A transformer 9 VAC can have a rectified voltage ~13-15 Volt DC )

lineup

[spence]

Thanks for the reply lineup! I will give the transformer/regulator option a try.

Best regards, Spence