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Liquid Sky -  Circuit Help

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andrelcg

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Hey guys,

Recently I built the Liquid Sky, based on the idea of rog8811(http://www.rog8811.com/liquidsky.htm) using a pc cooler , glass mirror  and 50mW green laser pen running at 3 volts. To adjust the speed of cooler and voltage of laser pen, I built a circuit based on TIP32, powered by 9 volts. I know! I should have used a trimpot! Was not available here at home.
The question is, TIP32 used to adjust the voltage of the laser pen can work dissipating the 6 volts constantly?

Hug,
Andre
 

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D

digital_blue

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IMO, you should have at least used a Mosfet or LM317. Also, I'm not sure you should be using a PNP transistor...
 
A

andrelcg

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digital_blue said:
IMO, you should have at least used a Mosfet or LM317. Also, I'm not sure you should be using a PNP transistor...
Click to expand...

If I use the LM317 will be overheating? Maybe I should use another source? :-?

Hug,
Andre
 
lasersbee

lasersbee

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andrelcg said:
[quote author=digital_blue link=1235957638/0#2 date=1235964495]IMO, you should have at least used a Mosfet or LM317. Also, I'm not sure you should be using a PNP transistor...
Click to expand...

If I use the LM317 will be overheating? Maybe I should use another source? :-?

Hug,
Andre[/quote]

We would need a circuit diagram (schematic) of your Speed controller... :cool:
And why should you have used a trimpot... :-?

Jerry
 
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andrelcg

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lasersbee said:
[quote author=andrelcg link=1235957638/0#3 date=1236012827]
Click to expand...
And why should you have used a trimpot... :-?

Jerry[/quote]

Because of the size!

Hug,
Andre
 

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digital_blue

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andrelcg said:
If I use the LM317 will be overheating? Maybe I should use another source? :-?
Click to expand...

The LM317 will not overheat if you're only using 9 volts, it should be fine without heatsinking. You will also need to configure the LM317 to regulate voltage instead of current. Just keep in mind that linear regulators dump the extra voltage as heat; the higher the input voltage(compared to the output), the more heat is generated...

Also, using PNP transistors may not work. They are "normally closed" and applying voltage to the base would cause it to turn off. 9V may be a bit too much on the base, you could be driving it beyond linearity and causing it to operate like a switch...
 
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kendon

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digital_blue said:
The LM317 will not overheat if you're only using 9 volts, it should be fine without heatsinking. You will also need to configure the LM317 to regulate voltage instead of current. Just keep in mind that linear regulators dump the extra voltage as heat; the higher the input voltage(compared to the output), the more heat is generated...
Click to expand...

shouldn't that be always (or when V[sub]in[/sub] is >3V) 3V?

and btw, what is "too hot" for the lm317? imo it is getting quite warm when touching it, but i have no idea how much would be too much...  :-?

//edit: nice work @andrelcg, what pointer (mw) did you use, and maybe you got some pics in action? :)
 
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andrelcg

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I could use the LM317 where R1=1k and R2=1.4k. Or use a trimpot in R2 to get 3V.

Hug,
Andre
 

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digital_blue

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shouldn't that be always (or when Vin is >3V) 3V?
and btw, what is "too hot" for the lm317? imo it is getting quite warm when touching it, but i have no idea how much would be too much...
Click to expand...

You will not be able to put 3V in and get 3V out, there is a dropoff voltage(a small voltage that is "lost" through the regulator). Too hot is when you burn your finger ;) If it's bearable, it's okay.
 
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andrelcg

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kendon said:
[quote author=digital_blue link=1235957638/0#6 date=1236026465]
The LM317 will not overheat if you're only using 9 volts, it should be fine without heatsinking. You will also need to configure the LM317 to regulate voltage instead of current. Just keep in mind that linear regulators dump the extra voltage as heat; the higher the input voltage(compared to the output), the more heat is generated...
Click to expand...

shouldn't that be always (or when V[sub]in[/sub] is >3V) 3V?

and btw, what is "too hot" for the lm317? imo it is getting quite warm when touching it, but i have no idea how much would be too much...  :-?

//edit: nice work @andrelcg, what pointer (mw) did you use, and maybe you got some pics in action?  :)[/quote]

Thanks kendon! I use a 50mW DX Green laser pen! Tonight I will post some pictures in action! :)

The operating temperature is 0 to 125 °C. Maybe until 100 °C may not a problem!

Hug,
Andre
 
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kendon

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andrelcg said:
The operating temperature is 0 to 125 °C. Maybe until 100 °C may not a problem!
Click to expand...

shame on me, could have looked into that data sheet myself... ::)

then i can stop worrying, it is way below 100°C since i didn't burn my finger (yet) touching it.
 
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andrelcg

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digital_blue said:
[quote author=andrelcg link=1235957638/0#8 date=1236028044]I could use the LM317 where R1=1k and R2=1.4k. Or use a trimpot in R2 to get 3V.

Hug,
Andre
Click to expand...

http://www.national.com/ds/LM/LM117.pdf

On the bottom of the first page, there should be a circuit. IMO, you shouldn't exclude the filter caps...[/quote]

Thanks for the tip and datasheet!

The values of R1 and R2 are correct for 3V of output?

Hug,
Andre
 
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andrelcg

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kendon said:
[quote author=andrelcg link=1235957638/0#10 date=1236028815]
The operating temperature is 0 to 125 °C. Maybe until 100 °C may not a problem!
Click to expand...

shame on me, could have looked into that data sheet myself...  ::)

then i can stop worrying, it is way below 100°C since i didn't burn my finger (yet) touching it.[/quote]

Yes! To have a good safety margin, the finger tip works!

Hug,
Andre
 
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andrelcg

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I tried the LM317 and still very warming! :(

What would be the best option in my case? Using a 3V transformer?

Hug,
Andre
 
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