Schematic Volt: to

Showing posts with label to. Show all posts

Showing posts with label to. Show all posts

Wednesday, November 19, 2014

3V to 40 Volt DC Converter Circuit

Switching regulator subsystems intended for use asdc to dc converters. 3V to 40 Volt DC Converter circuit | The use of switching regulators is becoming more pronounced over that of linear regulators because the size reductions in new equipment designs require greater conversion efficiency. Another major advantage of the switching regulator is that it has increasednapplication flexibility of output voltage. The output can be less than, greater than, or of opposite polarity to that of the input voltage.

The MC34063 series is a monolithic control circuit containing all the active functions required for dc to dcconverters. This device contains an internal temperature compensated reference, comparator, controlled duty cycle oscillator with an active peak current limit circuit, driver, and a high current output switch. This series was specifically designed to be incorporated in step–up, step–down and voltage–inverting converter applications. These functions are contained in an 8–pin dual in–line package.

FEATURES 3V to 40 Volt DC Converter :
· Wide Input Voltage Range 3 V to 40 V
· Precision Internal Reference 2%
· High Output Switch Current Up to 1.5 A
· Short-Circuit Current Limiting
· Adjustable Output Voltage
· Low Standby Current
· Oscillator Frequency Up to 100 kHz

Wednesday, November 12, 2014

6 V to 12 V Power Supply Inverter

This inverter circuit can provide up to 800mA of 12V power from a 6V supply. For example, you could run 12V car accessories in a 6V (British?) car. The circuit is simple, about 75% efficient and quite useful. By changing just a few components, you can also modify it for different voltages.

6 V to 12 V Power Supply Inverter Circuit Diagram

Part List:

R1, R4 2.2K 1/4W Resistor
R2, R3 4.7K 1/4W Resistor
R5 1K 1/4W Resistor
R6 1.5K 1/4W Resistor
R7 33K 1/4W Resistor
R8 10K 1/4W Resistor
C1,C2 0.1uF Ceramic Disc Capacitor
C3 470uF 25V Electrolytic Capcitor
D1 1N914 Diode
D2 1N4004 Diode
D3 12V 400mW Zener Diode
Q1, Q2, Q4 BC547 NPN Transistor
Q3 BD679 NPN Transistor
L1 See Notes
MISC Heatsink For Q3, Binding Posts (For Input/Output), Wire, Board

Friday, November 7, 2014

10 to 14W Class A Audio Amplifier

I have built this amplifier and it does sound good. It requires a preamp as it hasnt got much gain. It requires big heat sinks and a large transformer and a great power supply and careful wiring, but in the end it is xtremely simple and it sounds very good. The zener diode rejects any ripple coming from the power supply, But you still only want a ripple of 10mV max. The ripple reaching the input is amplified, so the zener diode gets rid of that, but whatever ripple there is will still reach the power stage.

Tuesday, November 4, 2014

How to Build a Electronic Telephone Ringer

How to Build a Electronic Telephone Ringer. This circuit produces a ringing sound similar to that made by more recent telephones. It consists of three almost identical oscillators connected in a chain, each generating a squarewave signal. The frequency of each oscillator depends on the RC combination: R4 and C1 around IC1.A, R8 and C2 around IC1.B and R12 and C3 around IC3.C.

The pairs of 100 kΩresistors divide the asym-metric power supply voltage (between 5 V and 30 V) so that, in conjunction with the 100 kΩfeedback resistors (R3, R7 and R11) either one third or two thirds of the supply voltage will be present at the non-inverting inputs to the opamps. The voltage across the capacitor therefore oscillates in a triangle wave between these two values.

Electronic Telephone Ringer Circuit Diagram:

The first oscillator is free-running at a frequency of approximately 1/3 Hz. Only when its output is high, and D1 stops conducting, can the second oscillator run. The frequency of the second oscillator is about 13 Hz, and optional LED D3 flashes when it is running. When the output of the second oscillator is low, the third is allowed to run. The frequency of the third oscillator is around 1 kHz, and this is the tone that is produced. The second oscillator is not absolutely necessary:

its function is just to add a little modulation to the 1 kHz tone. A piezo sounder is connected to the output of the third oscillator to convert the electrical signal into an acoustic one. The current consumption of the circuit is just under 1 mA with a 5V power supply, rising to about 1.65 mA with a supply volt-age of 15 V.

Sunday, November 2, 2014

3V DC to 5V DC REGULATED POWER SUPPLY ELECTRONIC DIAGRAM

3V DC to 5V DC REGULATED POWER SUPPLY ELECTRONIC DIAGRAM

A 5V DC regulated output from 2 cells 3V DC batteries. The output current of the circuit is limited to 50mA. However, it still able to supply many microcontroller circuits. 3009 and 560R Resistor provide the 5V DC output, make up a voltage divider network.

Friday, October 31, 2014

Digital Isolation up to 100 Mbits Diagram Circuit

When it is necessary to send a digital signal between two electrically isolated circuits you would normally choose an optoisolator or some form of transformer coupling. Neither of these solutions is ideal; optocouplers run out of steam beyond about 10 MHz and transformers do not have a good low frequency (in the region of Hertz) response. The company NVE Corporation (www.nve.com) produces a range of coupler devices using an innovative ‘IsoLoop’ technology allowing data rates up to 110 Mbaud. The example shown here uses the IL715 type coupler providing four TTL or CMOS compatible channels with a data rate of 100 Mbit/s. Inputs and outputs are compatible with 3.3 V or 5 V systems. The maximum isolation voltage is 2.5 kV and the device can cope with input transients up to 20 kV/µs.

Circuit diagram:

The company produce many other configurations including bidirectional versions that would be suitable for RS485 interfacing. The IsoLoop coupler is based on relatively new GMR (GiantMagnetoResistive) technology. The input signal produces a current in a planar coil. This current generates a magnetic field that produces a change in resistance of the GMR material. This material is isolated from the planar coil by a thin film high voltage insulating layer. The change in resistance is amplified and fed to a comparator to produce a digital output signal. Differences in the ground potential of either the input or output stage will not produce any current flow in the planar coil and therefore no magnetic field changes to affect the GMR material. Altogether the circuit provides a good electrical isolation between input and output and also protects against input signal transients (EMV).
Author: Gregor Kleine - Copyright: Elektor July-August 200

LM317 to create constant current of 2mA

I have a circuit where I want to have a constant current of 2mA through a variable resistor. Ive been told that I could probably use a LM317 as a current regulator, with one resistor on the ouput. But Ive read some places that the LM317 takes minimum 5-10mA load to function correctly.

How can I achieve a constant current output of 2mA when I dont know the resistance of the variable resistor?

The input voltage is about 2.755V. Output voltage doesnt matter, just the current.

Heres an image to my feeble attempt at a schematic:

enter

The LM317 with the single series resistor between output and adjust input is actually a fixed current source, not a current limiter. You dont need the LM317 to create a current limiter, a few discrete components will do:

enter

For a limiting at 2mA you select a 330Ω resistor for RSENSE. If there flows 2mA through it Q2 will start to conduct and reduce the base voltage of Q1, so that its current is cut off.

edit (re changed question)

Maybe youre focusing too much on the LM317. If you need a constant current you could use the LM234 which is a programmable current source for up to 10mA. You set the current with a resistor.

Wednesday, October 29, 2014

LM331 Frequency to voltage converter Diagram Circuit

Description.
LM331 is basically a precision voltage to frequency converter from National Semiconductors. The IC has a hand full of applications like analog to digital conversion, long term integration, voltage to frequency conversion, frequency to voltage conversion. Wide dynamic range and excellent linearity makes the IC well suitable for the applications mentioned above.
Here the LM331 is wired as a frequency to voltage converter which converts the input frequency into a proportional voltage which is extremely linear to the input frequency. The frequency to voltage conversion is attained by differentiating the input frequency using capacitor C3 and resistor R7 and feeding the resultant pulse train to the pin6 (threshold) of the IC. The negative going edge of the resultant pulse train at pin6 makes the built-in comparator circuit to trigger the timer circuit. At any instant, the current flowing out of the current output pin (pin 6) will be proportional to the input frequency and value of the timing components (R1 and C1). As a result a voltage (Vout) proportional to the input frequency (Fin) will be available across the load resistor R4.

Circuit diagram.

Notes.

The circuit can be assembled on a vero board.
I used 15V DC as the supply voltage (+Vs) while testing the circuit.
The LM331 can be operated from anything between 5 to 30V DC.
The value of R3 depends on the supply voltage and the equation is R3= (Vs – 2V)/ (2mA).
According to the equation, for Vs = 15V, R3=68K.
The output voltage depends on the equation, Vout = ((R4)/(R5+R6))*R1C1*2.09V*Fin.
POT R6 can be used for calibrating the circuit.

Sunday, October 26, 2014

3V to 40 Volt DC Converter Circuit

Switching regulator subsystems intended for use as dc to dc converters. 3V to 40 Volt DC Converter circuit | The use of switching regulators is becoming more pronounced over that of linear regulators because the size reductions in new equipment designs require greater conversion efficiency. Another major advantage of the switching regulator is that it has increasednapplication flexibility of output voltage. The output can be less than, greater than, or of opposite polarity to that of the input voltage.

The MC34063 series is a monolithic control circuit containing all the active functions required for dc to dc converters. This device contains an internal temperature compensated reference, comparator, controlled duty cycle oscillator with an active peak current limit circuit, driver, and a high current output switch. This series was specifically designed to be incorporated in step–up, step–down and voltage–inverting converter applications. These functions are contained in an 8–pin dual in–line package.

FEATURES 3V to 40 Volt DC Converter :
· Wide Input Voltage Range 3 V to 40 V
· Precision Internal Reference 2%
· High Output Switch Current Up to 1.5 A
· Short-Circuit Current Limiting
· Adjustable Output Voltage
· Low Standby Current
· Oscillator Frequency Up to 100 kHz

Saturday, October 25, 2014

Build 12V to 9V DC Converter

To get a more precise output voltage, replace zener diode Z1 with 10V and R1 with a 1Kilo ohm potentiometer. A Coolrib for Q1 is optional but highly recommended. You can replace Q1 for a more robust type to get more output amps depending on your requirements. Simple circuit to power your 9 volt cassette recorder and other stuff.

Parts List:

R1 = 560 ohm
C1 = 1000uF/40V, Electrolytic
C2 = 10uF/25V, Electrolytic
C3 = 330nF, Ceramic
Z1 = 9.1V, 1watt zener
Q1 = ECG184, NTE184

How To Build Regulated Power Supply with Stability at 3A

The circuit was designed to build a Regulated Power Supply with Stability at 3A will provide a regulated voltage from 40 V to 70 V in a 3 A current.

2N3055 – a complementary Silicon Epitaxial-Base planar NPN transistor mounted in Jedec TO-3 metal case for use as power transistor.
BD243 – an epitaxial-base Silicon NPN transistor intended for wide variety of high speed switching and power amplifier applications such as series and shunt regulators, and driver and output stages of high-fidelity amplifiers.
BC303 – a PNP silicon planar epitaxial transistor used for AF drivers & outputs, for AF medium power amplifiers, and for switching applications up to 1 A.

There are times when some applications are requiring a regulated power supply that has relatively high output voltage and stability. All of these features are being attained in the design of this circuit. The voltage output of the circuit can range from 40 V up to 60 V while carrying a current of 3 A while providing stabilization. The construction of the circuit is very simple since the components used were available easily in the market. The only thing that matters is how the connection will be ensured.

During the operation, when the circuit is delivering 50 V up to 60 V, the transistor Q1 will be hot enough and would require a large heatsink. For voltage output higher than 50 V up to 70 V, the stability of the circuit may be found unsatisfactory. This is the reason why the ideal output voltage of the circuit is 45 V up to 60 V. In order to alter the output voltage from 40 V up to 70 V, a 470 Ohms potentiometer RV1 is used for the adjustments. However, the potentiometer may also be replaced by two constant resistors with suitable values when the circuit adjustment has been done. This is due to the fact that the use of a potentiometer may lead to a 3 V of over voltage.

As a reminder, the positive output of the circuit should be connected at point A while the 0 V output should be connected at point B. The 0 V reference should not be connected to the ground for the circuit to function properly. the use of this 3 A power supply with an average of 50 V circuit may be found on various applications that normally requires this rating.

Since this type of circuit is easily built, it is being utilized in industrial, educational, clinical, and laboratory facilities. It may come with different additional features such as reduced ripple & noise, overload protection, and short circuit & high current protection.

Thursday, October 23, 2014

Build a Converter VGA to BNC Adapter

There are monitors which only have three BNC inputs and which use composite synchronization (‘sync on green’). This circuit has been designed with these types of monitor in mind. As can be seen, the circuit has been kept very simple, but it still gives a reasonable performance. The principle of operation is very straightforward. The RGB signals from the VGA connector are fed to three BNC connectors via AC-coupling capacitors. These have been added to stop any direct current from entering the VGA card. A pull-up resistor on the green output provides a DC offset, while a transistor (a BS170 MOSFET) can switch this output to ground. It is possible to get synchronisation problems when the display is extremely bright, with a maximum green component.

In this case the value of R2 should be reduced a little, but this has the side effect that the brightness noticeably decreases and the load on the graphics card increases. To keep the colour balance the same, the resistors for the other two colors (R1 en R3) have to be changed to the same value as R2. An EXOR gate from IC1 (74HC86) combines the separate V-sync and H-sync signals into a composite sync signal. Since the sync in DOS-modes is often inverted compared to the modes commonly used by Windows, the output of IC1a is inverted by IC1b. JP1 can then by used to select the correct operating mode. This jumper can be replaced by a small two-way switch, if required.

VGA to BNC adapter PCB layout

This switch should be mounted directly onto the PCB, as any connecting wires will cause a lot of interference. The PCB has been kept as compact as possible, so the circuit can be mounted in a small metal (earthed!) enclosure. With a monitor connected the current consumption will be in the region of 30 mA. A 78L05 voltage regulator provides a stable 5 V, making it possible to use any type of mains adapter, as long as it supplies at least 9 V. Diode D2 provides protection against a reverse polarity. LED D1 indicates when the supply is present. The circuit should be powered up before connecting it to an active VGA output, as otherwise the sync signals will feed the circuit via the internal protection diodes of IC1, which can be noticed by a dimly lit LED. This is something best avoided.

Resistors:

R1,R2,R3 = 470Ω

R4 = 100Ω

R5 = 3kΩ3

Capacitors:

C1,C3,C5 = 47µF 25V radial

C2,C4,C6,C7,C10 = 100nF ceramic

C8 = 4µF7 63V radial

C9 = 100µF 25V radial

Semiconductors:

D1 = LED, high-efficiency

D2 = 1N4002
T1 = BS170
IC1 = 74HC86
IC2 = 78L05

Miscellaneous:
JP1 = 3-way pinheader with jumper
K1 = 15-way VGA socket (female), PCB mount (angled pins)
K2,K3,K4 = BNC socket (female), PCB mount, 75Ω

Wednesday, October 22, 2014

How to Make a Frequency Generator

How to Make a Frequency Generator. On cloud busters Fredbuster created a wonder tutorial for getting started and building your own Zapper. Fredbusters Tutorial in PDF-Based off his design here is how I made my frequency generator.

Frequency Generator Circuit Diagram

Parts Needed

1 Project box with PC board included,

1 Compositor 1 micro farad, C2, I like the un-polarized because it allows you not to worry about positive an negative sides. If you do get one with a longer leg thats the positive, see schematic for proper placement.

1 Compositor .01 micro farad, C1

1 LED 1-3 volt, small red ones. Remember the longer leg is the positive, connect properly,

1 Resistor 3.3k ohm, R1, It will say it on the upper part figuring out the colors is a pain. See photo below for product ID.

1 Resistor 3.9k ohm R4

1 Resistor 4.7k ohm R5

1 Resistor 1k ohm R3 for creating a body zapper with pennies,

1 resistor for R2 see Fredbusters PDF file for specific resistor for frequency. I use variable potentiometers because I like to set exact frequencies myself. I use 100k potentiometers, they give me a range from 6hz to 460hz when adjusting. You can see in the below photo I have both the large audio and micro potentiometers. The micro is used to be set at 15hz and the Audio is for creating variable.

1 on/off switch for the battery

1 toggle switch for the switching between 15hzand variable. Thats how I like to do mine.

1 555CN timer chip, make sure its the one that can handle up to 18 volts. The CMOS 555 can only handle low voltage and is easily shorted out.

1 8 pin IC Socket, just incase you burn out your 555 you can replace it without creating another circuit.

2 9 volt battery plugs, I like 2 because it lasts longer and has more amperage. One will do fin though.

Black and Red 22 gauge connecting wire, Make sure its the one with multiple threads of copper and not a solid one. Its easier to bend and move. The solid copper connecting wire is to kinky and breaks to easily, for my taste.

1 spool of Solder, The thinner the better, for getting into tight spaces and heats up better.

1 Solder Iron, A pin point will be needed for this circuit.

1 1/8" audio phone jack, I like them because they make the box look clean and its and easy size to attach to any other devices.

First we take the PC board that was included with the Black box and break it into a size we need.

Next we place the 8 pin bracket in the middle.

Notice on the back how I bend over the pins to hold it in place.

Next we attach R1 3.3k resistor. One end goes to pin 8 and the other to pin 7, I bend the legs over the pin then cut off 1/4" longer than the distance to the pin. the remaining 1/4" I bent over and stick in the pin hole. see schematic.

Here is how it looks on the back.

Next we attach Compositor C2 1.0 mf, and Compositor C1 0.001 mf. C2 connects to pin 6 and the base of C1. C1 connects to pin 5 and C2 base.

Here is how it looks on the back, notice how the base of C1 and C2 are twisted together.

Next we add R4 3.9k and R5 4.7k to the board.

Notice on the back the ends are twisted together and connected to Pin 3.

Here is when I added the 555 timer, make sure the black dot is in the upper left corner.

Using one of the wire ends I cut off from the excess of the resistors I connect Pin 2 to Pin 6. like so.

Now is when I start adding the wires to hook up the positive and negative connections.

Back of circuit.

Now for the wires that hook up to LED, Output jack and switches.

You can see how I soldered the connections together. Make sure you are clean and accurate. Other wise a lose connection or overlapping solder will cause the circuit not to work. This takes patients and time, dont rush it. If you do overlap a connection with solder, heat it up, use another wire to suck up the excess and then use a knife to remove the last bits. I heat the wires first then add the solder. Its cleaner once you get used to soldering. Takes practice.

Here is what the final circuit looks like before its place in a box. You can see the R2 I added here. I use a toggle switch to go back and forth between the set resistor and variable resistor. One end of the resistor is connected to R1 where it attaches to pin 7. The middle Pin on the Potentiometer is then connected to a toggle switch. The Middle switch pin is then connected to C2 where it attaches to pin 6. Using potentiometers allows you to set a frequency you want. In Fredbusterstutorial he gives you the specific resistor for specific frequency.

Here are links to four photos showing detailed enlargement of the circuit with the variable potentiometers added and how they are connected. This should explain how I connected the potentiometers.

http://www.ryanmcginty.com/orgone/frontcircuitlg.jpg

http://www.ryanmcginty.com/orgone/backcircuitlg.jpg

http://www.ryanmcginty.com/orgone/beforeboxback.jpg

http://www.ryanmcginty.com/orgone/beforebox.jpg

Next I begin placing the circuit into the box. I slip the LED wires thru to the outside because thats how you hook up this specific light. I used shrink tubing to seal the connection keeping them not from touching other wires.

You can see how I drilled the holes to fit each switch, LED and output jack. This is how I have the circuit placed inside the box. Notice the blank area to hold the two 9 volt batteries. I prefer two 9v because it allow the Freq Gen to run longer. About 14 days nonstop at 15hz.

And finally how the frequency box looks when finished. Notice I dont have penny electrodes because this box is only to power OR devices and not kill body parasites. Copy the circuit drawing above and you can have both.

Radioshack sells a digital voltage meter which has a setting for frequencies. It cost me about $50. It works great. All I do is connect the output from the generator to the meter’s input wires. Instantly it says the exact frequency the dial is tuned too. If you don’t have voltage meter and work around the house repairing things yourself this is a must have.

To put the set the frequencies I use my computer. I use the 1/8" stereo jack into my sound card, making sure the input volume is on low. Use a Sound generator program and match the tones. Make sure the sound wave is set to square. It takes time to get it right but it works.

On a good day it takes me 1 hour and half to make the whole thing. It will cost you about $40 to 45 in parts to make one like mine.

Sourced By: Ryan

Thursday, October 9, 2014

Light to Frequency converter circuit

The circuit is based on TLC555, the CMOS version of famous timer IC NE 555. A photo diode is used for sensing the light intensity.The timer IC is wired in astable mode.The leakage current of the reverse biased photo diode is proportional to the light intensity falling on it.This leakage current charges the capacitance C1.When the capacitor voltage reaches 2/3 of the supply voltage the out put (pin 3) goes low.As a result the capacitor discharges through photo diode .When the capacitor voltage reaches 1/3 the supply voltage the out put (pin 3) of IC goes high.This cycling continues and we get a frequency at pin 3 proportional to the light intensity falling on the photo diode.

Light to Frequency Converter Circuit Diagram & Parts List.

Light

Light to Frequency Converter Circuit Diagram

Notes.

With the given components the frequency varies from 1KHZ @ complete darkness to 24 Khz @ bright sunlight.The frequency range can be changed by using different values for C1.
Use any general purpose photo diode for D1.

Improved 240 VAC TO 5 VDC POWER SUPPLY

This is simple way to power some 5v logic from a 240vac source. If a 120vac power adapter is used, the circuit will also work for 120vac power lines.

Sunday, October 5, 2014

How to calculate the value of a resistor using the color coded stripes on the resisto

To calculate the value of a resistor using the color coded stripes on the resistor, use the following procedure.

Step One: Turn the resistor so that the gold or silver stripe is at the right end of the resistor.

Step Two: Look at the color of the first two stripes on the left end. These correspond to the first two digits of the resistor value. Use the table given below to determine the first two digits.

Step Three: Look at the third stripe from the left. This corresponds to a multiplication value. Find the value using the table below.

Step Four: Multiply the two digit number from step two by the number from step three. This is the value of the resistor n ohms. The fourth stripe indicates the accuracy of the resistor. A gold stripe means the value of the resistor may vary by 5% from the value given by the stripes.

Resistor Color Codes (with gold or silver strip on right end)

Follow the above procedure with the examples below and soon you will be able to quickly determine the value of a resistor by just a glance at the color coded stripes.

Examples

Example1:
You are given a resistor whose stripes are colored from left to right as brown, black, orange, gold. Find the resistance value.

Step One: The gold stripe is on the right so go to Step Two.

Step Two: The first stripe is brown which has a value of 1. The second stripe is black which has a value of 0. Therefore the first two digits of the resistance value are 10.

Step Three: The third stripe is orange which means x 1,000.

Step Four: The value of the resistance is found as 10 x 1000 = 10,000 ohms (10 kilohms = 10 kohms).

The gold stripe means the actual value of the resistor mar vary by 5% meaning the actual value will be somewhere between 9,500 ohms and 10,500 ohms. (Since 5% of 10,000 = 0.05 x 10,000 = 500)

Example2:
You are given a resistor whose stripes are colored from left to right as orange, orange, brown, silver. Find the resistance value.

Step One: The silver stripe is on the right so go to Step Two.

Step Two: The first stripe is orange which has a value of 3. The second stripe is orange which has a value of 3. Therefore the first two digits of the resistance value are 33.

Step Three: The third stripe is brown which means x 10.

Step Four: The value of the resistance is found as 33 x 10 = 330 ohms.

The silver stripe means the actual value of the resistor mar vary by 10% meaning the actual value will be between 297 ohms and 363 ohms. (Since 10% of 330 = 0.10 x 330 = 33)

Example3:
You are given a resistor whose stripes are colored from left to right as blue, gray, red, gold. Find the resistance value.

Step One: The gold stripe is on the right so go to Step Two.

Step Two: The first stripe is blue which has a value of 6. The second stripe is gray which has a value of 8. Therefore the first two digits of the resistance value are 68.

Step Three: The third stripe is red which means x 100.

Step Four: The value of the resistance is found as 68 x 100 = 6800 ohms (6.8 kilohms = 6.8 kohms).

The gold stripe means the actual value of the resistor mar vary by 5% meaning the actual value will be somewhere between 6,460 ohms and 7,140 ohms. (Since 5% of 6,800 = 0.05 x 6,800 = 340)

Example 4:
You are given a resistor whose stripes are colored from left to right as green, brown, black, gold. Find the resistance value.

Step One: The gold stripe is on the right so go to Step Two.

Step Two: The first stripe is green which has a value of 5. The second stripe is brown which has a value of 1. Therefore the first two digits of the resistance value are 51.

Step Three: The third stripe is black which means x 1.

Step Four: The value of the resistance is found as 51 x 1 = 51 ohms.

The gold stripe means the actual value of the resistor mar vary by 5% meaning the actual value will be somewhere between 48.45 ohms and 53.55 ohms. (Since 5% of 51 = 0.05 x 51 = 2.55)

Other Resistor Information

There are some more rules that may be useful when working with resistors. You do not need to know them but if you need a resistor with a value that you do not have, you my be able to use the following information to create the value of resistor you need.

First Rule for Resistors : Series Connection

When two resistors are connected in series, as shown in Figure 1, the new resistance between points A and B is R1 + R2.

Figure 1

The resistors add together. For example if R1 = 500 ohms and R2 = 250 ohms then the resistance between points A and B would be R1 + R2 = 500 + 250 = 750 ohms.

Second Rule for Resistors : Parallel Connection

When two resistors are connected in parallel, as shown in Figure 2, the new resistance is smaller than either R1 or R2. The new resistance between points A and B is (R1 x R2) / (R1 + R2).

Figure 2

For example, if R1 = 500 and R2 = 250 then the resistance between points A and B = (500 x 250) / (500 + 250) = (125,000) / (750) = 167 ohms. If R1 = R2 then the new resistance is just R1 / 2.

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