I have decided to compile a list of the top ten most needed circuits that are a must know for anyone interested in DIY projects. These are the basics that can all be interchanged and used in conjunction with each other to make many of the projects that we all love so much.
10. The 5 v voltage regulator is a must, and is used to convert any 9v battery to the much needed 5 volts. This is used to power IC (integrated circuit) chips, as well as can be connected to a USB port to charge your ipod. The most common part is the 7805 chip, and here is the schematic.
9. Most projects require the use of an LED. This stands for a light emitting diode, and a diode only lets current go in one direction. It is important to put the LED into the circuit correctly or it won’t work. The longer lead is the positive lead, and must be placed in the circuit that way. theledlight.com gives an indepth tutorial on how to find the correct resistance values for different LEDs. Just remember the old equation V=IR (Voltage = Current * Resistance). For a nine volt battery a good 470 ohm resistor is a safe bet. Here is the simple circuit.
8. There are many times when a transistor is needed to be used as a switch. The NPN transistor can be used when the base is brought to a high voltage. The input current needs to be lower than the current through the collector (the top pin of the transistor). There is a 0.6 v drop accross the transistor, so the voltage accross the RB is going to be input voltage-0.6v. Go here for a more thorough explanation of picking the right resistor values.
7. There are many projects that require the use of USB, so it is important to know what the different pins of the USB are. This picture was found at networktechinc.com
6. There is much need for a simple audio amplifier. There are many ways to do this, one is to use a darlington transistor like my 1-watt amplifier, and another way is to use an opamp like my post on the CMOY pocket amplifier, but the best way is to use an LM386 chip. The different gains can be changed by changing the resistor values. C5 filters out the DC, and C4 and R1 act as a low pass filter. Go to warplink.com for the values to use for the comonents.
5. Often times when dealing with amplifiers you will need a low pass filter. This can be done with a simple RC circuit. To find the frequency that you are filtering, use the formula F=1/(2*pi*R*C)
4. If building a robot that follows a line, it is important to have an Infrared sensor and detector. You can read about this in my line following robot post.
3. Often it is necessary to use a simple NPN transistor as an amplifier. This is useful as a preamp for a microphone,
(Image from reconnsworld.com)
or even as a motor controller.
2. It is important to test your circuits before soldering anything together. Lots of times it is useful to have a powersupply that you can plug into the wall. Here is a circuit for building a 12v power supply. , this could be changed to a 5 volt power supply alsoThis is from a recent post of mine found at 12v power supply
1. It is often important to convert an AC signal to a simple DC signal. This can be done by using a rectifier. This can be found from a previous post of mine at AC-DC rectifier The diodes make the negative part of the AC sin wave positive, and the capacitor smooths out the ripples.
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