First of all examine APC (American Power Conversion) LAN surge protector. It is removed from some APC UPS.
The circuit is very simple. Diodes D1-D4 and D6-D9 are IN4006. The D5 diode is more interesting. It is 1.5KE6.8CA. This is special diode: 1500 WATT PEAK POWER TRANSIENT VOLTAGE SUPPRESSOR.
Note J3. On PCB it is small gap […]
If you want to build DVD/MP3/DivX/Xvid and etc. player you need only to design box. Take cheap power supply for +-12, 5 and 3.3V any DVD reading hardware and simple mainboard based on MTK1389 chip. Order MediaTek firmware and enter your logo… That’s all. This how this VIDO D403 DIVX player was made. The mainboard […]
For drilling wide holes in thin sheet metal I bought Irwin Unibit drill bit. It is self-starting drill.
For testing purposes I used steel sheet from ATX power supply box. Starting hole is a bit angular, next sizes are quite good. Only need to adjust the speed of the drill- to cut the steel, not grind.
In previous circuit, the temperature turn on the fan instantly. The regulation period is very short. To make it more wide just add only one resistor (R5):
While adjusting sensitivity of your schematics use potentiometer instead of R5. It must me about 100K … 1M range. After fine tuning, measure the resistance of potentiometer and replace […]
This small modification in the older schematics made it sensible to temperature.
Main difference from older circuit is that I used one of error comparators for NTC thermoresistor. R3 and R4 must be equal or something near to make temperature adjustments easy. As at this moment I have only one potentiometer at hand so I removed […]
It is simplest PWM fan speed control circuit from scrap. The detail values are not very critical.
Here is the schematics:
R1-~10K, R2-~100K, C1- 0.01μF, chip- TL494, KA7500. It would be good practice to put some electrolytic capacitor between Vcc and GND near the chip.
Using potentiometer R2 you can adjust fan speed.
While PWM?
MAJOR PRO: Almost no heat […]
In every schematic you can find few capacitors. Sometimes you remove old caps from some junk boards. And sometimes it is difficult to determine the cap value. There is some standards for cap coding, but not every manufacturer take care about it. The capacitance is measured in farads. But one farad is very […]
As I wrote in other article, we received some old Japanese made old hardware. On Friday I opened some big device and removed few more lamps.
This was power supply. And one heavy used and another quite new 6AS7. Also 5AR4 and 12AX7. The power supply was repaired in circa 1984. And one 5AR4 was replaced […]
|
Place for rent. |