Get 5V power from PC PowerSup.

[Guest PoRrEkE]

I need about 7 pins to be connected to 5V and I need about 11 pins to be grounded.Is it OK if I take 1 red wire and make it go past all the V pins ?Then take 1 black wire and make it go past all the ground pins ?Or should I try to use as many different red&black wires from this PSUP ?

[LawnDart 19]

Inside most PS power supplies, you'll find all the red wires bunched together and soldered to one common connector, and the same goes for all the yellow (12vdc) wires.Just be sure your current load doesn't exceed the power supply limits. You might be better off having multiple PS power supplies.Also, remember that most PS power supplies have a feature that doesn't allow them to turn on if there's no load sensed on the wires. So, if you turn it on with nothing connected to it, and it shuts off 1/2 second later, that's by design.Hope this helps!

[Guest PoRrEkE]

Aha, interesting, tnx.That's why my power sup from the 486 I have here seemed not to work. It does exactly that.Either way, I got an other PS from a friend who had one spare. The model name is "CWT-200PA" from the brand "target". Only page on google shows it should be a 200W PS, which sounds believable seen the model nr :)Scott Fausell suggests on his page to use 1 PS for the Photon interface so I think I can stick to this one.*quote*Power Supply: I recommend a single 20-30 ampere (145 - 350W) standard PC power supply. Use "Y" cables with floppy drive connectors to provide enough leads. +5v is always RIGHTmost pin. NEVER use yellow wire (+12v). If you are attaching less than 2 output modules you may need to place a 10 ohm load resistor across a +5v/GND pair in order to meet the minimum load requirements of the PS (Look here for instructions on how to do this). Please contact me if you have ANY questions prior to connectoing power. I cannot be repsonsible for damage to the board or yourself caused by improper power connections.*/quote*I have 4 output modules so I guess I should be safe then and just take 1 red wire and make it travel along all V inputs and 1 black travel along all the GND inputs. Then normally everything should be wired parallel.

[Guest Erups]

For a couple electronics a pc PSU is well overpowered: a bunch of electronic cards will at max use a couple amperes, while an old PSU can deliver in the order of 20 on the 5V and 12 on the 12V...So plenty of power for your use :)

[Guest PoRrEkE]

Aulraaight then.I will get back here soon I think to diskuss the "how to power up a led without interface (just hard wire it to a .. 5V power suply ?)"I am at the moment wiring up 1 of my displays. Thos one would be e.g. the NAV14 of the 5 segments are powered and changed by output board. The plan is to have the 1 in tront be ON all the time with the char "1" obviously.

[Guest spiliot_]

Getting a PC PSU to work might prove more difficult than one might think. These PSUs use electronics that work by sensing the current and voltage on the load and then trying to keep it constant.So where is the problem you ask? Well, they can't operate without sufficient load (in fact it is most common to burn one during startup where the load is not sufficient than with full or more load than it can handle).To use such a PSU you have to put a dummy load (like a big resistanse of enough Watts) to all its outputs (12V, 5V, 3.3V, -5V, -12V). The exact resistor value depends on the power you want to dissipate but I don't think that anything less than half will work...

[Guest Erups]

>To use such a PSU you have to put a dummy load (like a big>resistanse of enough Watts) to all its outputs (12V, 5V, 3.3V,>-5V, -12V). The exact resistor value depends on the power you>want to dissipate but I don't think that anything less than>half will work...I have to correct you here, a 0.1ohm resistor should do in many cases.There is no motivation for using a bigger one and disspate hundres of watts in the air...Anyway Philippe to connect just leds to the 5V use a 280ohm resistor, that allows for about 18mA to reach the led and that is ok for most leds, in case of blue or white leds, higher current may be required in such a case lower the resistor following this formula:Resistor value = Power voltage / Current neededSo that if you need 20mA at 5V that'sR = 5 / 0,02 = 250ohm

[Guest RichardL]

Here's a site that explains how to convert a PC power supply.. Works great.http://web2.murraystate.edu/andy.batts/ps/PowerSupply.htmRichard

[Guest PoRrEkE]

Wow, thnx :)So if I get this right, I can wire all my 20 LEDs up in parallel to eachother and connect a 280ohm resistor to the anodes of the led displays and then put the ground to the cathode. Then 5V to the resistors.Correct ?What if I want to wire the leds from the led display in serie ? Or is that not possible cuz they have CC ........ hmmz Guess that answers my question :(

[Guest Erups]

Hmmmm in series it is possible, but you have to take account for the voltage drop... 5v may not be enough for 20 leds...It is possible to wire them all in parallel, but resistor must be correctly dimensioned: 20 is about 2watt while standard resistors are rated at 1/4w... More leds may require higher wattage resistors.You may well wire them in bunches of parallel, like one resistor every 5 leds...

[Guest PoRrEkE]

H

[Guest Erups]

>the question. However, making "a bunch of parallels" of all>the leds used per display is an option, then wire the bunches>in series ..No, bunch in parallel>>But you say 5V may not be enough for 20 leds ?May not be enought for connecting them in series.Basically every electronic component when used causes a voltage drop.Power in the more bigger sense, is composed by voltage and current.And components need both.So if you make a line of voltage dropping elements, you end up with not enough voltage for the next element.This usually happens when wiring in series; when wiring in parallel what is affected is current not voltage.So you prefer the parallel way rather then the series way.Almost always....

[Guest PoRrEkE]

check ;)