Ajutor sursa de alimentare

Cred ca poti gasi o discutie pe tema asta undeva pe forum. Chiar asta era problema, cu caderea de tensiune la sursele de calculator si cum se face sa ramana minim 12 sa poata functiona incarcatoarele pe la casa omului...
In final ideea era ca se pot modifica putin niste reglaje, sa scoata mai mult de 12V. Ba unele mai vechi au chiar un semireglabil pe acolo cu care le duci pana pe la 13,5-14V. Trebuie cautata schema de principiu a sursei pe internet, vazut circuitul care face munca aia urata cu "scosul" celor 12V, cautata apoi documentatia acelui circuit integrat si schimbata o rezistenta cu alta sau cu una semireglabila. Am mai fazut discutii pe alte pagini legate de aceeasi probleme dar in engleza. Ideea era cam aceeasi, ca surse se gasesc des, sunt ieftine si destul de bune. Sau mai e varianta sa cauti o sursa, care ramane cu mai mult de 12V sau care se poate regla usor, daca ai de unde alege.

PS. Am vazut si eu ca uneori chiar cu consumator pe 12V crestea tensiunea de la 11,7V in gol la 12,5V in sarcina. Posibil cu ceva pe 5V (cum zicea Sir_Vaska) sa fie si mai bine. Oricum, nu-i chiar asa de greu.

Aceasta postare a fost editata de bitex: 13 October 2004 - 10:14 PM

Si mai trebuie pus la masa firul violet.

" Trebuie sa faci un scurt intre doi pini in soclul care intra pe placa. Parca era firul violet cu inca unul de langa el (parca un GND), dar nu merg cu presupusul in continuare, ca nu-mi mai amintesc totul. Gasesti pe net schema conectorului cu informatiile necesare. Daca vrei sa caut eu, spune-mi. Sau asteapta pana apare un butonar inrait care le-a memorat... Oricum, chiar daca mergi la intamplare, nu strici nimic in sursa.

Pentru pornire pune la masa firul verde.

Yank out the power supply and with a simple mod, you have a cheap 12.5-13.5 volt power supply. There are lots of wires coming out of the PS when you take it out of the computer. Snip off all wires at board except 6 black, 2 red & 4 yellow wires. Solder the 4 yellow wires together for a 12.5-13.5v HOT lead, Solder 4 black wires together for the GROUND, Next solder the other two black wires together for a 5v GROUND, Solder the two red wires together for a 5v HOT, solder the 5 volt hot and ground to a 3 ohm 20W resistor or (2 10W wired parralel) and mount the resistor/s to the vent in the P/S case so it will "sink" some of the heat and be in-line with the air flow from the blower. This will put about a 1 amp load on the 5 volt section and allow the regulator to work. If the power supply you have has a pot to adjust output, you can turn it up to 13.5v MAXIMUM out put (any more and you will stress the traces on the board) this will also increase the 5v a little but not much. If yours dosen't have a adjustment you can change the output by changing resistor values in the circut but you are on your own as to what will work as there is no "set" standard as how the manufacturer designs the circut. A 400W PC power supply will make a 20 amp continuous switching power supply. IF you pick up RF noise from the supply you can wrap the yellow hot lead about 15 turns through a torid and this should solve the problem. Use your prefference on a power switch and terminals. I used the switch from the old computer, a couple of 1/4" X 1 1/4" long bolts and drilled out a set of knobs from a old car sterio for insulators.NOTE If using bolts for the terminals, file off the shinny coating on top of the head before soldering the wires to the bolts. Total cost...$1.89(I had to buy the resistor). Add some rubber feet to the bottom if you want. Not bad for a small power supply

Converting a PC Switching Power Supply to 13.5V

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This information was published by VK2EVB, Peter McAdam, in the December 2001 edition of Lo-Key #72 (CW Operators' QRP Club Inc.). As I have done nothing but reproduce his results, all the credits and kudos belong to VK2EVB.
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Introduction
Power supplies from old personal computers are "a dime a dozen," so to speak. Go to any hamfest/computer show and you will find tables of them. I can get all I want from a local computer vendor who has stacks of old "useless" computers. Typically, these power supplies produce outputs of +12V/9A, -12V, +5V/20A, -5V. VK2EVB's circuit converts the +12V line to +13.5V. By keeping the original rectifier in the +12V line one ends up with a +13.5V/9A power supply. (VK2EVB swapped the 20A rectifier from the +5V line with the 8A version in the +12V line to end up with a supply rated at +13.5V/15A.) I choose to keep the 9A rectifier in line and not do the swap as I do not need a high current capability while running QRP.

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Doing the Conversion

Use Care When Working on the Power Supply as the AC Mains Lines are Exposed When Opening the Enclosure!!! Unplug the power supply when working on it and put it back together before testing it!!!
The process is fairly simple and straight forward (refer to the schematic below).
Basically VK2EVB removed three resistors from the power sampling circuitry, and added one.
1. Start by removing all but one output lead from the +12V line and the GND line. Keep the leads with the largest wires. These will serve as the output lines to whatever jack you supply.
2. Trace Pin 1 from the TL494 through the 27k resistor (R33) to the +12V line, and insert a 2k2 resistor in series with the +12V output and R33.
3. Trace Pin 1 from the TL494 through the 4k7 resistor (R32) to the +5V line and remove the resistor.
4. There is also on that same line a 470R (R21) and a 270R (R20), going from the +5V trace on the board to -5V and -12V respectively. Remove both of these resistors.
5. Secure the circuit board back into the enclosure and plug in the AC line. You should see +13.5V where formerly there was +12V. (I didn't, at first! I had removed the wrong resistor and ended up with about +8.8V!)
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Improving the Filtering
1. Typically there is a 2200uF/16V electrolytic from the +12V output pad to GND. VK2EVB replaced that capacitor with two 2200uF/25V electrolytics. I didn't have those values in my junk box so I replaced the original capacitor with a 6800/35V electrolytic instead. Remember to observe the polarity of the capacitors!
2. VK2EVB also installed a filter in the output line of the now +13.5V supply to remove any stray radiation from the AC mains. He used a PI filter consisting of two 0.047uF capacitors and a 100uH inductor using a ferrite core from another junk supply. I didn't install the filter, but I did install a similar RF choke in series with the +13.5V output line. I used a ferrite core from an old computer power cord, winding as much insulated 18AWG stranded wire through it as I could. I ended up with about 550uH.
3. A 220 ohm resistor was also added across the output +12V and GND terminals to serve as a load for the supply, attempting to keep the noise to a minimum. VK2EVB used a 1 watt resistor; I used a 2 watt carbon composition.
4. VK2EVB also soldered desoldering braid on top of the +12V traces to improve current handling capability. I chose not to do this since I didn't swap the 9A and 20A rectifiers (see the note above).

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Almost Finished!
1. In my supply there were two holes where the original output wiring and computer on/off switch wires exited the enclosure. These holes were on the end of the enclosure opposite the fan and AC jack. The end of the enclosure was slotted for ventilation.
2. I bolted a rectangular piece of circuit board on this back side of the enclosure, using the slots for screw holes, and mounting two banana plug terminals in the space provided by the larger holes.
3. I also enlarged one end of one ventilation slot to accept an SPST toggle switch. (This switch should be rated for the AC line current and it should be installed in one of the AC lines coming into the power supply. Use fairly heavy wire.)
4. VK2EVB also installed a power on indicator LED. He picked up +12V for the LED from the original +5V circuit board pad which after the conversion is at about +12V.
5. Stick four rubber feet on the bottom of the enclosure and test the supply at various frequencies while listening on your radio. Hopefully, you'll hear only signals and background noise, and no spurious signals from the switching supply.

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My Results
My converted supply output is +13.49V/9A and, thus far, I haven't heard any unwanted signals from the power supply itself. The conversion took me about 2 hours to complete. Have fun and credit VK3EVB for a fun homespun project!
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http://www.qsl.net/a.../PC-Supply.html

Am vorbit cu electronistul care ma ajuta pe mine la toate cele lumesti... Sursele AT pot fi modificate sa scoata pana la aproximativ 13,5V sau oricum, sa nu scada tensiunea sub 12V. Apare pe YM cu ID-ul: srv_pub. Puteti lua legatura si direct cu el. Eventual spuneti ca stiti ID-ul lui de la mine. Cred ca va poate ajuta cu mult mai multe (de la surse la monitoare, camere video, etc).

evrika
pe pinul 1 al integratului 494 se inseriaza un semidereglabil de 10 k
urmarea:se poate regla tensiunea de iesire pana pe la 20 Vcc
n-am incercat mai sus dar cred ca mergea
am pus ca sarcina un bec halogen de masina 12v/55w si am reglat din nou semidereglabilul
pentru ca cazuse tensiunea pe la vreo 11 v
Concluzia:reglat in gol la 14 vcc cade in sarcina de 4,5A la 12,6 vcc
perfect pentru familia mea!!! ""

Aceasta postare a fost editata de Se poate si asa ?: 14 October 2004 - 01:41 AM

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