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rollerband
3rd Oct 2005, 12:13 AM
How to get 24Vdc, beside using batteries.. I got a small pc fan, about the size of a 60mm x 60mm, with fan Diameter 55mm. pls advise anyway to get it stepdown from main source, or any long lasting batteries recommended . Thks

silane
3rd Oct 2005, 10:47 AM
You can:

- get an ac to DC adaptor that can supply up to 24V, but hard to find, usually is 12V max
- put 2 12V adaptor to connect in series to get 24V
- use a PC power supper
- DIY a power supply with simple parts like step down transforms, diode and capactors. I will write something on DIY of power supply in Library.

dom
3rd Oct 2005, 03:20 PM
I got my 24V adapter from the electrical shop. Those selling cables, batteries, adapter do selling it. From the adapter, you are able to adjust to use 12V or 24V...

NanoDave
4th Oct 2005, 01:31 AM
You can:

- get an ac to DC adaptor that can supply up to 24V, but hard to find, usually is 12V max
- put 2 12V adaptor to connect in series to get 24V
- use a PC power supper
- DIY a power supply with simple parts like step down transforms, diode and capactors. I will write something on DIY of power supply in Library.

Yes please!! especially also regulated and unregulated power supply because I find unregulated ones are much cheaper and was wondering whether they can be used for peltier...

NanoDave
4th Oct 2005, 01:33 AM
How to get 24Vdc, beside using batteries.. I got a small pc fan, about the size of a 60mm x 60mm, with fan Diameter 55mm. pls advise anyway to get it stepdown from main source, or any long lasting batteries recommended . Thks

If you can't find the adapter why not chuck it and get a common 12v fan.. it's less than $5 at SLT and you'll save a lot of legwork and headache.. :)

rollerband
4th Oct 2005, 01:30 PM
I have 2 of this fans, so looks like using a pc power supply is more economical. At the same time, I can use it to build a new PC tower, and able to place a nano tank next to it. Looks ideal....
So jus to confirm, PC power supply does supply 24Vdc? gotta check it out ..

silane
5th Oct 2005, 10:11 PM
So jus to confirm, PC power supply does supply 24Vdc? ..

It does. :)

silane
5th Oct 2005, 10:16 PM
Yes please!! especially also regulated and unregulated power supply because I find unregulated ones are much cheaper and was wondering whether they can be used for peltier...

Unregulated one is fine to be used on peltier, peltier can take a bit of ripper in the voltage, as long as there is no large voltage drop when large current is drawn.

NanoDave
6th Oct 2005, 01:29 AM
Unregulated one is fine to be used on peltier, peltier can take a bit of ripper in the voltage, as long as there is no large voltage drop when large current is drawn.

I see thanks!!! thats great news :D

Will it have a big impact on performance compared to regulated ones? :)

jojoecute
6th Oct 2005, 09:43 AM
Don't worry U still can use 12V DC adaptor to run the fan...




How to get 24Vdc, beside using batteries.. I got a small pc fan, about the size of a 60mm x 60mm, with fan Diameter 55mm. pls advise anyway to get it stepdown from main source, or any long lasting batteries recommended . Thks

silane
6th Oct 2005, 07:34 PM
I see thanks!!! thats great news :D

Will it have a big impact on performance compared to regulated ones? :)

See this, unregulated power supply:
http://my.integritynet.com.au/purdic/power1.html

Choose the center of the ripple to be the voltage you want, then choose a small ripple value, like 2%. Use it to calculate value of C1.

So for a 24V power supply, the max would be 24.24V and min is 23.76V, with 2% ripple. Since the ripple is alternating 100 times per second (50Hz x 2), the peltier is operating at 1% above performance at one cycle, and 1% below performance at the other, average out, no performance hit. :D Give a calculation of what is the value of C1 you need, to drive a high performance (high current also) peltier, C1 needed may be too big.


More info:
Power Supply design - 1 (http://my.integritynet.com.au/purdic/power1.html) - a home learning tutorial on the basics of designing simple
power supplies for radio projects.

Power Supply - 2 (http://my.integritynet.com.au/purdic/power2.html) - regulation of power supply voltages.

Power Supply - 3 (http://my.integritynet.com.au/purdic/power3.htm) - designing with solid state regulators as well as using higher current regulators.

Power Supply - 4 (http://my.integritynet.com.au/purdic/power4.htm) - a bench variable voltage power supply project for you to construct at home.

rollerband
6th Oct 2005, 07:53 PM
Very technical, very informative..... Good for DIY, or school mini project .. :D But thks .. very educating too.

xtrekker
7th Oct 2005, 12:43 PM
How to get 24Vdc, beside using batteries.. I got a small pc fan, about the size of a 60mm x 60mm, with fan Diameter 55mm. pls advise anyway to get it stepdown from main source, or any long lasting batteries recommended . Thks

you can easily construct a linear regulator using the the following components

1. Setdown Transformer
2. Bridge rectifier
3. 1 x 2200uF E-Cap
4. 1 x LM7824 Linear regulator
5. Small piece of strip board

Cost me less then $3 for the above components excluding the transformer and the soldering equpiment which i aredi have on hand. Do a search on LM7824 datasheet. The instructions and schematics should be inside the datasheet.

cheers