I realized that some people might be interested in this...
All of the parts are available for under $4, and could even be found in old electronics lying arond, how I did it.
Just wondering if anyone would be interested in this.
I noticed that Alan had one, but it is rated at 300mA... Many fans will not require that amount, but close. If you want more than 1 fan, you definately need a higher rating. Also, all motors spike when they first turn on, drawing much more than 300mA... 2A=2000mA, should definatley cover that. A 1A version is just as easy and you save a wopping $.24 at the place I was looking...
Let me know
All of the parts are available for under $4, and could even be found in old electronics lying arond, how I did it.
Just wondering if anyone would be interested in this.
I noticed that Alan had one, but it is rated at 300mA... Many fans will not require that amount, but close. If you want more than 1 fan, you definately need a higher rating. Also, all motors spike when they first turn on, drawing much more than 300mA... 2A=2000mA, should definatley cover that. A 1A version is just as easy and you save a wopping $.24 at the place I was looking...
Let me know
Yeah Dwiel they would be very interesting 😀
I'd appreciate if you post a quick schematic - as I'm sure others would.
Also I was looking at your projector on your site, and I was wondering if all 3 of the fresnels you use are dual (split/not split???) Just seems like a lot of fresnels if they're not split.
I'd appreciate if you post a quick schematic - as I'm sure others would.
Also I was looking at your projector on your site, and I was wondering if all 3 of the fresnels you use are dual (split/not split???) Just seems like a lot of fresnels if they're not split.
Ace: I will go ahead and write the quick tutoiral.
Mr. Kh: They are split. I got one unsplit with my OHP. I split it, and realized that it wasn't big enough for my 15" LCD. doh... So I bought a bigger one that could 'see' the entire screen. Unfortunatly, the focal lengths on the larger lens was really big, 11" and 9", so I just made the first focal length shorter by putting one of the small lenses in there. (the most unwarped one... as both were fairly warped)
Mr. Kh: They are split. I got one unsplit with my OHP. I split it, and realized that it wasn't big enough for my 15" LCD. doh... So I bought a bigger one that could 'see' the entire screen. Unfortunatly, the focal lengths on the larger lens was really big, 11" and 9", so I just made the first focal length shorter by putting one of the small lenses in there. (the most unwarped one... as both were fairly warped)
Is it ok if I just put it up on my website?
I can email it to ya if you want, but the website is easier for EVERYONE to access. Also, this way, I can update it if, god forbid, anyone finds discrepincies in my writing 😉. I'm working on it right now, and will post as soon as it is up on the web.
Thanks for your interest!
I can email it to ya if you want, but the website is easier for EVERYONE to access. Also, this way, I can update it if, god forbid, anyone finds discrepincies in my writing 😉. I'm working on it right now, and will post as soon as it is up on the web.
Thanks for your interest!
Ok, I have it posted on my site. Its at the top of the DIY home page.
Let me know what you think.
It is probobly wordy, as that is how I tend to write, before some outside editing. I would actually be more disapointed if I didnt recieve any suggestions on how to make it more clear, where to fix grammer, etc.
Thanks!
Hopefully, everyone should be able to build their own power supplies now...
I would put pictures and step by step instructions for those who know nothing about electronics, because I dont have a camera. I was borrowing some one elses for all of the other ones and had to give it back yesterday 🙁. If someone would be up fr taking pictures as they build their PSU, I would be very happy to include them, in the tutoiral to make it easier for people to assemble.
Let me know what you think.
It is probobly wordy, as that is how I tend to write, before some outside editing. I would actually be more disapointed if I didnt recieve any suggestions on how to make it more clear, where to fix grammer, etc.
Thanks!
Hopefully, everyone should be able to build their own power supplies now...
I would put pictures and step by step instructions for those who know nothing about electronics, because I dont have a camera. I was borrowing some one elses for all of the other ones and had to give it back yesterday 🙁. If someone would be up fr taking pictures as they build their PSU, I would be very happy to include them, in the tutoiral to make it easier for people to assemble.
Good power supply plans!
The only problem with it is that if you add more fans the voltage will drop under 12 V and if you only have one fan the voltage will maybe be over 12V, this is why they call this type of powersupply unstabilized, a simple way to correct this is to add a LM7812 on the output. With a LM7812 on the output you can use the powersupply to more electronics stuff like tft and more. But there is nothing wrong with the powersupply without the LM7812 but measure the voltage over the fans so you don´t destoy them.
The only problem with it is that if you add more fans the voltage will drop under 12 V and if you only have one fan the voltage will maybe be over 12V, this is why they call this type of powersupply unstabilized, a simple way to correct this is to add a LM7812 on the output. With a LM7812 on the output you can use the powersupply to more electronics stuff like tft and more. But there is nothing wrong with the powersupply without the LM7812 but measure the voltage over the fans so you don´t destoy them.
I have made these measurements already:
Voltage out of transformer: 12V AC Great
DC Voltage after bridge rectifier: 10.5V DC (low due to the wave form not really being DC)
DC Voltage after capacitor: 11.8V DC Great
I will go ahead and include that in the tutoiral. Thanks. I will also make sure that there is an extra diode protecting the regulator to prevent reverse voltage.
What you are saying makes sence. You say that this kind of supply generates the correct voltage when no load is applied, but will vary depending on the load that it is suppling?
Thanks for the tip, I'll go ahead and put that in the tutorial soon.
Voltage out of transformer: 12V AC Great
DC Voltage after bridge rectifier: 10.5V DC (low due to the wave form not really being DC)
DC Voltage after capacitor: 11.8V DC Great
I will go ahead and include that in the tutoiral. Thanks. I will also make sure that there is an extra diode protecting the regulator to prevent reverse voltage.
What you are saying makes sence. You say that this kind of supply generates the correct voltage when no load is applied, but will vary depending on the load that it is suppling?
Thanks for the tip, I'll go ahead and put that in the tutorial soon.
Heya Dweil, normally in 12v psu's you use a 16v ac transformer, the bridge rectifier will alway's break this down to about 13.5v/14v, you then use a suitible electrolitic cap for stabilisation, then after the cap a fuse, then after the fuse a 12v voltage regulator to only have 12v coming out of the dc rails, a power diode for polarity protection and your set.
If the transformer is putting out only 12v we have a problem, under load you will never acheive 12v, you will need to have atleast 2volts more on the transformer to compensate the load on the output otherwise the more amps you draw the more the voltage will drop. A smoothing cap over the mains input can also help take away noise and unstability in the ac line.
Thanks for the info, but i was kind of hoping this was a fancy electronic psu (comp psu) with high power regs and a smoother circut.🙂
Trev
If the transformer is putting out only 12v we have a problem, under load you will never acheive 12v, you will need to have atleast 2volts more on the transformer to compensate the load on the output otherwise the more amps you draw the more the voltage will drop. A smoothing cap over the mains input can also help take away noise and unstability in the ac line.
Thanks for the info, but i was kind of hoping this was a fancy electronic psu (comp psu) with high power regs and a smoother circut.🙂
Trev
Oh, sorry about the disappointment. I was trying to show people who didnt know much about electronics how to make a simple PSU. I will add some more components to make it more smooth, as that is what people are more interested in. 😉
Dweil, I think your transformer with 12V AC will work really good, I don´t know how you have measured the DC voltage it should be higher. This is how the output voltage should be: 12 V* 1.41 = 17 V, 17 - 1.4V (diods) = 15.5 Volt DC after the cap unloaded.
Where are you getting the 1.41 multiplier?
Also, fans do not need 'perfect' DC do they? I was running of a the AC transformer and bridge rectifier and they worked... not at maximum output, but they worked nonetheless. Do you think it would be good if I tried putting the output through an osciloscope? They have them at school that I could try out. Will a voltage regulator really help that much?
I will measure the voltages again sometime later, although, I have the transofrmer/bridge rectifier ciruit in a hard to get to position... Its all electrical taped together in a kind of ball 😉 Didnt have any circuit boards...
Also, fans do not need 'perfect' DC do they? I was running of a the AC transformer and bridge rectifier and they worked... not at maximum output, but they worked nonetheless. Do you think it would be good if I tried putting the output through an osciloscope? They have them at school that I could try out. Will a voltage regulator really help that much?
I will measure the voltages again sometime later, although, I have the transofrmer/bridge rectifier ciruit in a hard to get to position... Its all electrical taped together in a kind of ball 😉 Didnt have any circuit boards...
Converting an AC output wall adapter to DC
Where a modest source of DC is required for an appliance or other device,
it may be possible to add a rectifier and filter capacitor (and possibly
a regulator as well) to a wall adapter with an AC output. While many wall
adapter output DC, some - modems and some phone answering machines, for
example - are just transformers and output low voltage AC.
This is also the simplest and safest way to construct a small DC power supply
as you do not need to deal with the 110 VAC at all.
To convert such an adapter to DC requires the use of:
* Bridge rectifier - turns AC into pulsating DC.
* Filter capacitor - smooths the output reducing its ripple.
* Regulator - produces a nearly constant output voltage.
Depending on your needs, you may find a suitable wall adapter in your junk
box (maybe from that 2400 baud modem that was all the rage a couple of years
ago!).
Considerations:
* An AC input of Vin VRMS will result in a peak output of approximately
1.4 Vin - 1.4 V. The first factor of 1.4 results from the fact that the
peak value of a sinusoid (the power line waveform) is 1.414 (sqrt(2))
times the RMS value. The second factor of 1.4 is due to the two diodes
that are in series as part of the bridge rectifier. The fact that they
are both about 1.4 is a total coincidence.
Therefore, you will need to find an AC wall adapter that produces an output
voltage which will result in something close to what you need. However,
this may be a bit more difficult than it sounds since the nameplate rating
of many wall adapters is not an accurate indication of what they actually
produce especially when lightly loaded. Measuring the output is best.
* Select the filter capacitor to be at least 10,000 uF per 1000 mA of output
current with a voltage rating of at least 2 x Vin. This rule of thumb will
result in a ripple of less than 1 V p-p which will be acceptable for many
devices or where a voltage regulator is used (but may be inadequate for
some audio devices resulting in some 120 Hz hum. Use a larger or additional
capacitor or a regulator in such a case.
* Suitable components can be purchased at any electronics distributor as well
as Radio Shack. The bridge rectifier comes as a single unit or you can put
one together from 1N400x diodes (the x can be anything from 1 to 7 for these
low voltage applications). Observe the polarity for the filter capacitor!
The following examples illustrate some of the possibilities.
* Example 1: A typical modem power pack is rated at 12 VAC but actually
produces around 14 VAC at modest load (say half the nameplate current
rating). This will result in about 17 to 18 VDC at the output of the
rectifier and filter capacitor.
* Example 2: A cordless VAC battery charger adapter might produce 6 VAC.
This would result in 6 to 7 VDC at the output of the rectifier and filter
capacitor.
Adding an IC regulator to either of these would permit an output of up to
about 2.5 V less than the filtered DC voltage.
Where a modest source of DC is required for an appliance or other device,
it may be possible to add a rectifier and filter capacitor (and possibly
a regulator as well) to a wall adapter with an AC output. While many wall
adapter output DC, some - modems and some phone answering machines, for
example - are just transformers and output low voltage AC.
This is also the simplest and safest way to construct a small DC power supply
as you do not need to deal with the 110 VAC at all.
To convert such an adapter to DC requires the use of:
* Bridge rectifier - turns AC into pulsating DC.
* Filter capacitor - smooths the output reducing its ripple.
* Regulator - produces a nearly constant output voltage.
Depending on your needs, you may find a suitable wall adapter in your junk
box (maybe from that 2400 baud modem that was all the rage a couple of years
ago!).
Considerations:
* An AC input of Vin VRMS will result in a peak output of approximately
1.4 Vin - 1.4 V. The first factor of 1.4 results from the fact that the
peak value of a sinusoid (the power line waveform) is 1.414 (sqrt(2))
times the RMS value. The second factor of 1.4 is due to the two diodes
that are in series as part of the bridge rectifier. The fact that they
are both about 1.4 is a total coincidence.
Therefore, you will need to find an AC wall adapter that produces an output
voltage which will result in something close to what you need. However,
this may be a bit more difficult than it sounds since the nameplate rating
of many wall adapters is not an accurate indication of what they actually
produce especially when lightly loaded. Measuring the output is best.
* Select the filter capacitor to be at least 10,000 uF per 1000 mA of output
current with a voltage rating of at least 2 x Vin. This rule of thumb will
result in a ripple of less than 1 V p-p which will be acceptable for many
devices or where a voltage regulator is used (but may be inadequate for
some audio devices resulting in some 120 Hz hum. Use a larger or additional
capacitor or a regulator in such a case.
* Suitable components can be purchased at any electronics distributor as well
as Radio Shack. The bridge rectifier comes as a single unit or you can put
one together from 1N400x diodes (the x can be anything from 1 to 7 for these
low voltage applications). Observe the polarity for the filter capacitor!
The following examples illustrate some of the possibilities.
* Example 1: A typical modem power pack is rated at 12 VAC but actually
produces around 14 VAC at modest load (say half the nameplate current
rating). This will result in about 17 to 18 VDC at the output of the
rectifier and filter capacitor.
* Example 2: A cordless VAC battery charger adapter might produce 6 VAC.
This would result in 6 to 7 VDC at the output of the rectifier and filter
capacitor.
Adding an IC regulator to either of these would permit an output of up to
about 2.5 V less than the filtered DC voltage.
Adding an IC regulator to a wall adapter or battery
For many applications, it is desirable to have a well regulated source of
DC power. This may be the case when running equipment from batteries as
well as from a wall adapter that outputs a DC voltage or the enhanced adapter.
The following is a very basic introduction to the construction of a circuit
with appropriate modifications will work for outputs in the range of about
1.25 to 35 V and currents up 1 A. This can also be used as the basis for a
small general purpose power supply for use with electronics experiments.
What you want is an IC called an 'adjustable voltage regulator'. LM317 is one
example - Radio Shack should have it along with a schematic. The LM317 looks
like a power transistor but is a complete regulator on a chip.
For the LM317:
1. R2 = (192 x Vout) - 240, where R2 in ohms, Vout is in volts and must be at
between 1.2 V and 35 V.
2. Vin should be at least 2.5V greater than Vout. Select a wall adapter with
a voltage at least 2.5 V greater than your regulated output at full load.
However, note that a typical adapter's voltage may vary quite a bit
depending on manufacturer and load. You will have to select one that
isn't too much greater than what you really want since this will add
unnecessary wasted power in the device and additional heat dissipation.
3. Maximum output current is 1 A. Your adapter must be capable of supplying
the maximum current safely and without its voltage drooping below the
requirement in (2) above.
4. Additional filter capacitance (across C1) on the adapter's output may help
(or be required) to reduce its ripple and thus the swing of its input.
This may allow you to use an adapter with a lower output voltage and reduce
the power dissipation in the regulator as well.
Using 10,000 uF per *amp* of output current will result in less than 1 V
p-p ripple on the input to the regulator. As long as the input is always
greater than your desired output voltage plus 2.5 V, the regulator will
totally remove this ripple resulting in a constant DC output independent
of line voltage and load current fluctuations. (For you purists, the
regulator isn't quite perfect but is good enough for most applications.)
Make sure you select a capacitor with a voltage rating at least 25% greater
than the adapter's *unloaded* peak output voltage and observe the polarity!
Note: wall adapters designed as battery chargers may not have any filter
capacitors so this will definitely be needed with this type. Quick check:
If the voltage on the adapter's output drops to zero as soon as it is pulled
from the wall - even with no load - it does not have a filter capacitor.
5. The tab of the LM317 is connected to the center pin - keep this in mind
because the chip will have to be on a heat sink if it will be dissipating
more than a watt or so. P = (Vout - Vin) * Iout.
6. There are other considerations - check the datasheet for the LM317
particularly if you are running near the limits of 35 V and/or 1 A.
Trev
For many applications, it is desirable to have a well regulated source of
DC power. This may be the case when running equipment from batteries as
well as from a wall adapter that outputs a DC voltage or the enhanced adapter.
The following is a very basic introduction to the construction of a circuit
with appropriate modifications will work for outputs in the range of about
1.25 to 35 V and currents up 1 A. This can also be used as the basis for a
small general purpose power supply for use with electronics experiments.
What you want is an IC called an 'adjustable voltage regulator'. LM317 is one
example - Radio Shack should have it along with a schematic. The LM317 looks
like a power transistor but is a complete regulator on a chip.
For the LM317:
1. R2 = (192 x Vout) - 240, where R2 in ohms, Vout is in volts and must be at
between 1.2 V and 35 V.
2. Vin should be at least 2.5V greater than Vout. Select a wall adapter with
a voltage at least 2.5 V greater than your regulated output at full load.
However, note that a typical adapter's voltage may vary quite a bit
depending on manufacturer and load. You will have to select one that
isn't too much greater than what you really want since this will add
unnecessary wasted power in the device and additional heat dissipation.
3. Maximum output current is 1 A. Your adapter must be capable of supplying
the maximum current safely and without its voltage drooping below the
requirement in (2) above.
4. Additional filter capacitance (across C1) on the adapter's output may help
(or be required) to reduce its ripple and thus the swing of its input.
This may allow you to use an adapter with a lower output voltage and reduce
the power dissipation in the regulator as well.
Using 10,000 uF per *amp* of output current will result in less than 1 V
p-p ripple on the input to the regulator. As long as the input is always
greater than your desired output voltage plus 2.5 V, the regulator will
totally remove this ripple resulting in a constant DC output independent
of line voltage and load current fluctuations. (For you purists, the
regulator isn't quite perfect but is good enough for most applications.)
Make sure you select a capacitor with a voltage rating at least 25% greater
than the adapter's *unloaded* peak output voltage and observe the polarity!
Note: wall adapters designed as battery chargers may not have any filter
capacitors so this will definitely be needed with this type. Quick check:
If the voltage on the adapter's output drops to zero as soon as it is pulled
from the wall - even with no load - it does not have a filter capacitor.
5. The tab of the LM317 is connected to the center pin - keep this in mind
because the chip will have to be on a heat sink if it will be dissipating
more than a watt or so. P = (Vout - Vin) * Iout.
6. There are other considerations - check the datasheet for the LM317
particularly if you are running near the limits of 35 V and/or 1 A.
Trev
No they do not need perfect DC, it will work fine with your circuit and if you got to high voltage just add some diods in serie with the fans. A voltageregulator is only needed if you don´t know how much load you have.
A voltage regulator regulates the power so u will only have the power you need kept at a certain level, (in the case of having too much), its just like a regulator on a gas bottle, same thing but with power.
Trev
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