AC-DC (no not the hardrock-countrytrance-techno band)

[polar bear6]

hey
if a babymonitor is power from a walloutlet (AC) can it run on DC?
because i dont like it when the babymonitor is in plugged in the wall, its to wired (get it, wired).

and another thing, should i post the pics from all the stuff i bought?
i kinda figured that it was a "dead" topic...

[cjwillms]

I'm not 100 % sure about this, but devices like that usually have a power brick (big buldge in the plug or wire), or then have a internal converter. These basically converts the AC to DC with a combination of capacitors, diods, resistors, and voltage regulators.

If you can, take a multimeter and connect it to the where the power cord comes into the baby monitor. Once you know what voltage it's running at, you should be able to rig a battery up to it.

[Admin]

Yea, there should be a power adaptor that converts from AC to DC. Usually the adaptor tells you required input and output voltage/current/power, etc. This is that big brick thing that cjwillms mentioned. If there is no external thing, get out your screwdriver and multimeter . . .

To be wireless, all you need to do is to recreate that output DC voltage with a battery and voltage regulator.

Keeping around a set of power adaptors with different voltages are useful for future hacking - dont trash it!

[polar bear6]

there is no external AC-DC converter. and the only thing inside i can see that is remarkable is a big thing, it makes the
220V AC to 11V AC.

i have a picture here, its the big thing in the right corner:
http://img525.imageshack.us/my.php?image=babycallbigweelgmsgistrippedca.jpg

and i have another pic of it, its in the bottom right corner:
http://img525.imageshack.us/my.php?image=loot25gt.jpg

ye ye what the heck Ill post the other pics of my stuff to in case you wanna see 
http://img525.imageshack.us/my.php?image=gms8tj.jpg
http://img525.imageshack.us/my.php?image=irextendertankgmmacpowersupply.jpg
http://img525.imageshack.us/my.php?image=liionbatterisgicamerasmousegut.jpg
http://img525.imageshack.us/my.php?image=loot19fh.jpg

if you wanna know anything about the pictures just ask, and i really wanna know if someone know how to use those cameras i have...  stupid SGI couldn't be friends with the normal PC's had to make their OWN type of stuff so people will get angry and not buy their stuff... GARR!

Keeping around a set of power adaptors with different voltages are useful for future hacking - dont trash it!

yea i try to save them, i have 2 full buckets off them now, all fom 3-30V mostly DC, think i have 1 AC...
my mom freaks out tho, not good, not good at all!

stupid SGI

[Admin]

so that big thing is a transformer, and is probably hooked up to other circuit stuff to output DC. check around it for a DC voltage. there is a good chance you will find the supplying DC voltage across that giant blue capacitor in the picture. if so, just remove the transformer and apply that same DC voltage across that capacitor.

[cjwillms]

Really nice haul.

From what I can tell, it looks like your SGI camera is useing a CMUcam . This link may prove to be useful, but I'm not really sure
http://www.cs.cmu.edu/~cmucam/gallery.html

[polar bear6]

so i just de-solder the capacitator and put +11,1V on where it used to be the capacitators + pole, and then take my ground wire thingy and put it on the ground of the schemetic... right?

will it work with 12V?

[Admin]

Ummm no keep the capacitor, but remove the transformer.

My theory is that the large capacitor is part of the AC to DC circuit, helping to smooth out the DC voltage to a constant voltage. It would be the last step. But there are probably more electronics between the transformer and capacitor, perhaps a regulator or diode or something. See if there is. Basically trace the wires.

When your device is turned on, see what the voltage is across the capacitor. That would be the voltage you need to replicate (if my theory is correct). It should be less than the 11V on the transformer.

You could also probably apply a DC voltage directly where the transformer wires are after removing the transfer. But I have no idea what will happen if you apply a DC voltage to an AC to DC converter input . . . Perhaps apply 11V DC? No idea. 

Just apply a small voltage and just keep increasing the voltage until the capacitor has the voltage it normally has under AC voltage.

And it will work under 12V if there is a regulator somewhere in the circuit. Since batteries are a volt or two over the rated voltage when fully charged, it would be a good idea to add an 11V regulator since I doubt this device has one.

g'luck!

[Botanic]

To me it looks as if there are four diodes underneath the two pinkish white and one red cable. I could be wrong since the picture is not so good.
But if they are diodes and four of them, it is definetly a simple AC/DC converter.

In that case, just plug it in and measure the voltage across the big capacitor. Then remove the cap and cut the wires between the diodes and the cap.Then solder one plus and one minus cable to where the cap used to be.
The capacitor is not needed if it is fed with DC from a battery.

[Admin]

Botanic, yea that makes sense.

As for the capacitor, I would perfer to keep the cap simply because it acts as a good energy buffer. Of course for a battery connection you dont need a cap even half that big for supression, but why remove it if its already there?

[Botanic]

As for the capacitor, I would perfer to keep the cap simply because it acts as a good energy buffer. Of course for a battery connection you dont need a cap even half that big for supression, but why remove it if its already there?

Because there are always losses over components. There is a resistance inside the cap. That resistance does a small loss. Very small, and will not probably make a huge difference.
Also removing the cap would give two nice holes to solder the battery holder into.

[polar bear6]

so basically what i do is to desolder the cap and the diodes (since the diodes wont be of much use right? and it seems so hard and much work to cut the wires on the PCB.) and apply the voltage the is on the cap when its plugged in. its 13V on the cap but i will use 12 because its easier

thanks a lot for all the help 

To me it looks as if there are four diodes underneath the two pinkish white and one red cable. I could be wrong since the picture is not so good.
But if they are diodes and four of them, it is definetly a simple AC/DC converter.

you were right,  it is 4 of them, see here on the pic, its a closeup, but the wires are over them but you see the leads.

http://img503.imageshack.us/my.php?image=closeupbabycall3ro.jpg

[Botanic]

You got it right 

If you want to make the thing lighter, you can trace the wires on the PCB back from the diodes and remove anything before them. Everything before the diodes will be useless.

[zamboniman60]

it usually goes:
[mains power] ==> [step-down transformer] ==> [diode bridge] ==> [reservoir capacitor] ==> [voltage regulator]

if you just put in 12-14 volts where the transformer was, the regulator circuit could handle any surplus probably.