WorkBench Dual Power Supply

I will just explain part of this circuit. D9 and D10 provide a low cost -1.4 from -5 V. This is needed to reach near 0.00 for LM317 Min. setting. An LED also can be used with proper bias. Note that there is a Temperature Coefficient in ppm, see The Unusual Diode FAQ. but it may not matter upto 8 bits accuracy.

TIP2955, TIP3055 (NPN), TIP2955 (PNP) Complementary Silicon Power Transistors. It is a Darlington, that means good current gain. See Darlington transistor – Wikipedia. When current in R1 10E goes more than 50mA a voltage of 50mA X 10E = 500mV is applied across Emmiter-Base junction. So lower than 500mV no bias the tap is turned off, 500mV-700mV the tap starts turning on depending on type of transistor. The transistor is like a water Tap. So TIP2955 carries the major current burden thru the load allowing LM317 to do the decision making when to turn-on or off. It is analog control, it is not On-Off but linear-proportional. The LM317 is very cool as the burden is passed off to TIP2955 who will need a heatsink to keep going and deliver the power you want.

WorkBench Dual Power SupplyPut the filter caps appropriately. The Hum-Noise will be filtered. The cap after the regulator should be a small guy. The main filter cap after the Bridge can be as big as your cabinet or budget.

If you build it and wire it without designing a PCB, then make all wiring and connection very sound. The test of this ability you can know easily, If your project stops working after the last screw of the cabinet is tightened, Then we need to improve.

  • Analog Blind Dial On Delay TimerAnalog Blind Dial On Delay Timer
    It is called analog dial timer as it has no digital display, but the chip is digital it is CD4541. It is Mains operated, you [...]
  • Transistor Beta and Vce Tester
    This was a Beta Hfe and Vce Measuring Instrument used in Incoming Inspection of Power Transistors made by me 16 years back. Custom Built Test [...]
  • Regulated Power Supply 30V 5A
    This is a Regulated 0-30 V DC Power Supply manufactured by me in small numbers, 0-30V 5A and 5V -5A. It had a Switching Preregulator. [...]
  • Mains Voltage monitor using LM3914
    This Circuit helps in the monitoring of mains supply voltage. It does not use a isolation step down transformer. This has to be constructed only [...]
  • Multi Output Instrument Power Supply
    Every electronic gadget primarily needs a D.C, power supply to energize it. It also forms the basic requirement for any constructional project. consequently there is [...]
  • Relay Driver – Electromagnetic
    This circuit is a standard way of driving Small Power Relays from Control Signals generated by Logic or Opamp Circuits. C2 and R5 form a [...]
  • PLL using 4046 – Phase Locked Loop
    CD4046 is a PLL or phase lock loop, it mainly consists of a VCO and phase comparators. This is a component in FM demodulation and [...]
  • Analog Mux for Data Acquisition Systems
    Here is a 4-20 mA In/Out Analog Mux with Cascade option. This is a simple circuit i designed to make a Automation System within a [...]
About delabs 160 Articles
Product Design - Industrial Automation and Instrumentation. -