LM317 output to 0v

Description As you may recall the LM317 regulator is adjustable from 1.25 to about 35v. By adding 2 diodes you can drop the voltage slightly, about 0.6v of a voltage drop across each diode, so in the schematic below you can get close to 0v Schematic Parts List QTY PART-REFS VALUE --- --------- ----- Resistors --------- 1 R1 220R Capacitors ---------- 2 C1,C3 100nF 1 C2 100uF 1 C4 10uF Integrated Circuits ------------------- 1 U1 LM317T Diodes ------ 2 D1,D2 1N4004 Miscellaneous ------------- 1 RV1 5k

Adjustable 7805 DC output

Description You can, with a little modification use a 7805 regulator to generate a variable voltage output, in the example below the output can be 5v to 30v. At higher output voltages you should fit a suitable heatsink to the 7805. Schematic Parts List QTY PART-REFS VALUE --- --------- ----- Resistors --------- 1 R1 220R Capacitors ---------- 2 C1,C3 100nF 1 C2 100uF 1 C4 10uF Integrated Circuits ------------------- 1 U1 78L05 Miscellaneous ------------- 1 RV1 5k

9v to 5v DC PSU

Description This is a basic 9v to 5v PSU using a 7805 regulator, this was a common circuit to build for building a low cost 5v stabilised DC supply using a 9v PP3 battery as an input source Schematic Parts List QTY PART-REFS VALUE CODE --- --------- ----- ---- Capacitors ---------- 2 C1,C2 1nF 2 C3,C4 1uF Integrated Circuits ------------------- 1 U1 7805

Book Light

Description A simple book light Schematic Bill of materials QTY PART-REFS VALUE CODE --- --------- ----- ---- Resistors --------- 1 R1 150K 1 R2 120R 2 R3,R4 100K Capacitors ---------- 1 C1 10nF 1 C2 220uF Transistors ----------- 1 Q1 NPN 1 Q2 PNP Diodes ------ 1 D1 3V Bulb Miscellaneous ------------- 1 BAT1 3V 1 SW1 Push Button switch

Basic DC PSU

This is a basic DC power supply using the 78XX voltage regulator. Schematic Parts List QTY PART-REFS VALUE --- --------- ----- Capacitors ---------- 1 C1 1000uF 1 C2 100uF Integrated Circuits ------------------- 1 U1 78XX Miscellaneous ------------- 1 BR1 BRIDGE RECTIFIER 1 FU1 3A Fuse 1 TR1 TRAN-2P2S - 115v primary / 24 v secondary

LM317 Basic example

This is the most basic example of using a LM317 voltage regulator. The variable resistor (R1) and R2 are used to select the output voltage. The Lm317 is capable of delivering up to 1A of output current depending on the type you have.The input voltage can be up to 40V and output voltage can be adjusted from 1.2V to 37V. In our example we recommend 28v max. A heat sink must be fitted to the LM317 where the output current exceeds 250 milliamps. Bill of materials QTY PART-REFS VALUE --- --------- ----- Resistors --------- 1 R1…

Flashing led circuit

Description A simple LED flasher using a 555 timer Schematic Bill of materials Resistors --------- 2 R1,R3 1k 1 R2 470k Capacitors ---------- 1 C1 1uf Integrated Circuits ------------------- 1 U1 555 Diodes ------ 1 D1 DIODE-LED

Fundamental Digital Gates

There are 5 basic digital gates used to perform Logic Operation and these are called a Buffer, NOT, AND, OR, XOR Basic Logic Gates Symbol Mathmatical Formula Truth Table Buffer Q = A A Q 0 0 1 1 NOT Q = NOT A A Q 0 1 1 0 AND Q = A . B A B Q 0 0 0 0 1 0 1 0 0 1 1 1 OR Q = A + B A B Q 0 0 0 0 1 1 1 0 1 1 1 1 XOR Q = A + B A B Q 0 0 0 0 1 1 1 0 1 1 1 0

SMD resistors

All surface mount resistors have a 3-digit or 4-digit code. Here is a picture of a 3-digit surface mount resistor The first and second figures indicate the significant figures and the third one, is the multiplier. As an example, if the SMD resistor has the figures 102, it indicates 1, 0 = 10 x 102 ohms. That is the value is 1K. This next example can catch people out at first , 100 is not in fact a 100 ohm resistor but is in fact a 10×100 = 10 ohms or 10×1 = 10 ohms. In the case of resistors less than 10 ohms, the…