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# Laser display made in 15 minutes (video)

#### Pontiacg5

##### New member
Diodes, capacitors and a pulsed input makes high voltage. It could be done

#### Benm

##### Well-known member
The actual increase from a (very big) capacitor in average voltage is 1.41 (root 2) times. So if you started with 10 volts AC, it would rectify into 14.1 volts DC, minus the losses in the diodes (0.7v each, ending with 12.7 volts).

There are -different- circuits that use capacitors and diodes as voltage multipliers as well, and those can be used to increase voltage as far as practical limits permit.

A voltage douber is very easy to build, but it runs at half frequency so it needs bigger capacitors compared to the normal bridge rectifier.

#### JordanRHughes

##### New member
Drunk people make dumb comments in the background. Ignore them.

Description explains how we threw it together.

YouTube - Home built laser show

Thanks for the share. I want to d that sort of thing. How much to get started? Thanks in advance.

Jordan.

#### Tech_Junkie

##### Banned
I'm genuinely curious how a cap would increase voltage rather than what I described. Could you explain this to me?
I second Jay's question, as far as I know you cannot rely on just a capacitor to increase the voltage going through a circuit. You CAN hook up capacitors in series to increase maximum working voltage, but that is completely irrelevant.

Regards,

amk
Electronics 101:

A capacitor behind the bridge rectifier will increase the -average- voltage going to the load, in this case making the motor run faster.

Without the capacitor, the output from the bridge rectifier are a series of half-sine waves between zero volts and the peak voltage. If you put a capacitor over the output that will charge to the peak voltage, and power the motor while the voltage from the bridge is below peak. When it hits the next peak, the capacitor will be recharged.

The capacitor needs to be big enough to make the voltage drop due to it discharging into the motor small. Also, the transformer must be able to supply the peak current at the top of each sine wave - mostly not a problem with small systems.

#### amkdeath

##### New member
Rofl I lol'd at that picture TJ

Regards,

amk

#### Tech_Junkie

##### Banned
That's an oldie, like me. :yh:

#### bloompyle

##### 2
@ that more you know pic, that was an epic win! I haven't heard that term used in a while :crackup: Thanks for makin me smile

#### Jayls5

##### New member
Thanks for the share. I want to d that sort of thing. How much to get started? Thanks in advance.

Jordan.
It's really hard to quantify this sort of thing. I'm the kind of guy who rips things apart and stores things for future possibilities. I got an industrial filtered variable DC power supply from a garage sale for \$5, which powered many of the lasers. We ordered a bunch of "5mW" reds in bulk for other laser builds at a very low price (using for other purposes originally). We had silicon diodes... cheap on ebay. Breadboard, couple dollars. Home amplifier (varies). Played with a 30mW green keychain laser on it, about \$10. We are in the process of buying 50mW A/C powered and self cooled lasers for constant application. Basically, the idea is, play with SIMPLE household things for awesome effects. For example, I just ripped apart an old phone that wasn't being used: has a tiny DC vibrating motor in there that adds crazy effects.

I had a few old as busted laptops that I ripped the hard drive disks from... perfect mirror reflectors. We have other things in our bay of goodies to make fun effects, but this video was seriously just dicking around with minimalistic parts.

Here is a quick picture to try to explain it a little better.

The black line would be your voltage, the capacitor will store the voltage and dissapate it over the low spot as the voltage switches over. The bigger the capacitor the longer it can cover and "fill" the hole. The green lines in this picture are voltage after capacitors, and the capacitors are getting bigger the further right you go.

Its a crude drawing, but I think it gets the point across. The capacitors won't increase voltage, but help make it more uniform at a higher voltage than it would be without them.

Bingo. I know I wasn't the one with the electrical engineering degree, but his claims seemed completely incompatible with the devices function. A capacitor won't increase voltage unless it was charged and then wired in series (which would cause a direct increase in voltage just like a battery in series, disregarding capacitance).

He seemed to be describing the schematic you drew, which I immediately considered and deemed undesirable. It would smooth out the immediate stops of the D/C motor, making bass notes less responsive in the spin (or however else you design it) in a laser display.

#### Coeysesdfa

##### New member
Pretty cool,you do it better than me.i tried to do a laser show with my friends long before,but failed,not very beautiful!