A resistor obeys Ohm's law (V=IR); the current through it is equal to the voltage across it divided by the resistance (equivalently \$I=\frac{V}{R}\$)

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53 views

Are there any effective estimates for up-rating resistors power capability by adding airflow?

I'm considering using a bank of resistors similar to this: http://www.vishay.com/docs/31842/fve.pdf 300-400 watt "corncob" wirewound resistors. I understand that they can be run over their spec'd ...
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2answers
1k views

Why is the first band on a resistor never black?

I'm taking an electronic circuit analysis class, and I was asked to give the color of the 3rd band of a 1MΩ resistor. My answer was blue, thinking it could be black-brown-blue (01 * 1MΩ), but the ...
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3answers
101 views

Electronics I problem

Suppose that Vin= -∞, that forces D1 to open(OFF) and D2 to close (ON). Given E is 2 , then Vout=-2. Then I applied KVL to find the equation for Vd1 ( Off). Now I know that I have to find the ...
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3answers
49 views

Choosing the right voltage divider by load

I'm using an Android IOIO board to detect simple digital pulses from a 12v source. The input pins are 5V tolerant. Would a simple voltage divider work in this situation? I guess my concern is whether ...
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5answers
318 views

Pulsing an LED with no series resistor

I have a basic circuit using a BJT common emitter which I have constructed to pulse a red LED on to use as a strobe with 1us ON time (@12V) and plenty of time to cool down (<< 1% duty cycle). ...
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1answer
69 views

Conductive magnet to read resistor value?

I want to know if I can hook-up a resistor to one part of a Magnet Snap (carried by SparkFun), then another magnet snap to analog-pin on Arduino and still be able to read resistance value? Is this ...
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2answers
84 views

Arduino and resistors

So , hopefully this is my last question on this system it's about the connections: about the transistor, i want to use it like a switch, so i wanted to know how to determine the value of the ...
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2answers
72 views

LED resistor calculator wrong?

Planning to use a green LED (forward voltage 2V, forward current 30mA) on a 12V circuit so using as resistor calculator (led.linear1.org/1led.wiz) I bought a 390 ohms, 1W resistor. However after ...
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1answer
30 views

Selectively outputting 2 inputs based on a third input

I currently have 2 inputs that can be on or off, they could be 00, 01, 10, or 11. I want to output them only if a third input is active. I figured BJT transistors would do the job, but they seem ...
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3answers
76 views

Obtaining a specific resistance

first of all, let me apologise for my inexperience with electronics. Now that's over with, I'm trying to follow a guide that specifies the use of a specific temperature sensor with an output of 5v ...
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2answers
47 views

Hooking up an 8x8 LED board

I recently bought this 8x8 LED board from geeetech which came with this datasheet. I'm new to programming so I bought this board to "figure it out" but now I'm running into issues I don't understand. ...
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8answers
710 views

When does the placement of a resistor matter?

I've been a programmer for years but am very new to electronic engineering. So far I see people saying it doesn't matter where a resistor goes in your LED circuit as long as it is present, but it ...
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1answer
35 views

Load resistor value for phototransistor switch

According to this application note from Fairchild (btw, I find Fairchild's application notes to be of immense value - thanks to all who have taken the time to write one), the load resistor value for a ...
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1answer
33 views

Programmable Unijunction Transistor Circuit

I am currently teaching my self electronics and have a question about PUTs. I am wondering why there has to a resistor on both sides of the PUT in this circuit: Please note that I have already read ...
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3answers
82 views

What is the voltage source and ground on an antenna?

I've seen a few diagrams relating to AM demodulation, and I can't for the life of me figure out where the voltage source and ground come from in an antenna. From what I understand, an antenna can ...
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2answers
87 views

How to Design a schematic for 8-LED Logic Circuit and Turn them on in pairs? [closed]

I'm trying to design the schematic of an 8-LED logic circuit and turn them on in pairs according to the following sequence: 1 - 8, 2 - 7, 3 - 6, 4 - 5, 5 - 4, 6 - 3, 7 - 2, 8 - 1 ,i used ...
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3answers
94 views

LED Resistor Choice with changing voltage

I'm planning on adding leds to a small quadcopter which runs on a 1s lipo battery. I am planning on attaching the leds straight to the battery rather than the regulated voltage the main circuit board ...
0
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1answer
34 views

Resistor programming of a boost converter, check my understanding?

I'm looking at the datasheet for a TPS6103 boost converter, and trying to figure out how to configure it for 5V 1A output. The datasheet is not making this easy to understand. Datasheet: ...
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1answer
47 views

Current division and power delivery to resistors

I am trying to get the resistor e in this circuit to consume the most power possible by changing its resistance. It seems 100 ohms is just about right, a little less or more and it's power consumption ...
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1answer
124 views

Trouble with very first circuit

I'm building an assembly that will drive some infrared LEDs. Although the final product will use three, I'm just playing with one for testing purposes at the moment. The spec sheet for the LEDs I'm ...
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3answers
64 views

Determine saturation base current from NPN transistor datasheet (or what resistor do I need to ensure saturation?)

The Fairchild 2N3904 has a long data sheet(https://www.fairchildsemi.com/datasheets/MM/MMBT3904.pdf) so let's use that for this exercise. I'm interested in using an NPN in common emitter ...
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2answers
52 views

EMC, resistors and trimpots

I trying to get EMC certification and stumbled upon problem. In the above circuit, they will apply ESD to the exposed part of the trim pot, and it permanently changes the value of the trim pot and ...
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5answers
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Does using a resistor in series on a breadboard track work as expected?

I've read up on Kirchhoff's laws of current, however I'm not certain how it applies in this case. I have 1 10K resistor in series on a breadboard track. Considering that electrons flow the path of ...
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2answers
39 views

Energy Absorption By Series Resistance During Cap Charging

This question formed while trying to size a NTC thermistor to limit the inrush current to a capacitor. Assume the schematic below (with a fixed resistance): simulate this circuit – ...
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2answers
105 views

Different LEDs in parallel

Are there any special considerations I should pay attention to, when I wire multiple LEDs in Parallel? I am doing a project with a 100 LEDs in parallel. Each LED could be a different color, and each ...
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3answers
69 views

Can I use 1 resistor for both inputs of an RTL NOR gate?

I am working out the ideal RTL NOR circuit to use as universal gates for a large project. Based on what I've found on Wikipedia, to implement a NOR gate using BJTs and resistors, we have the ...
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0answers
28 views

DHT11 remote sensing — which resistor?

According to the DHT11 data sheet here: http://www.micropik.com/PDF/dht11.pdf, on wire runs longer than 20m, one should use a 'different' pull-up resistor from Data to VCC. What should the value be, ...
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2answers
61 views

Minimum burden resistor for current transformer

In calculating a burden resistor for a current transformer, what determines how low a value you can use? Assuming you can still obtain the minimum voltage acceptable to the ADC, what other factors ...
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0answers
39 views

how to wire up 2 separate ultrasonic transducers

Okay I have 2 separate receiver and transmitter and i've seen this post and it does tell me how to hook up. But why do I need all the transistors and resistors? Why cant I just use the 5v pin, ground ...
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5answers
548 views

Does this TO-220 Package Resistor need a heatsink?

I purchased this 0.5 Ohm power resistor, which comes in a TO-220 Package, with the aim of pushing 3A through it (i.e. 4.5W) The datasheet has the following information: It says it will rise 6.5 ...
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2answers
96 views

How to power a 12V6A peltier device with a 14.4V battery?

How to power a 12V6A peltier device with a 14.4V battery. My son is working on a school science project and unfortunately I have very little knowledge on electrical engineering. Please be patient ...
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4answers
82 views

Analyzing an op amp circuit (transfer function) that does not match the basic cases

At the following circuit I want to find what it does and basically its transfer function. I've searched a lot but I didn't find any circuit like this. Since it does not match any of the basic types of ...
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1answer
111 views

Resistor colour code chart [closed]

China has recently changed the colour code for resistors.I searched on google but it didn't show the real value of the Chinese 4 band resistor.Please help!!!
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0answers
64 views

How much resistance should a pull resistor include? [closed]

How much pull to ground resistance do I need? Is the amount you need variable? How did you figure this out? (Where can I learn too) Any references I should look to? So sorry for my large host of ...
0
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0answers
34 views

What is the current output of a typical piezo element?

I'm trying to sense vibration using a piezo. To protect my MCU from damage, I plan on using a zener diode/resistor combo like below: simulate this circuit – Schematic created using ...
0
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1answer
72 views

Calculate resistors for LED

I bought some bead LEDs with these specs.: Voltage: DC 3.4~3.6V Power: 3W Light Color : Cool White Electric current: 350-600MA I have an Arduino powered by a 9V battery. I'd like to connect 10 LED ...
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3answers
259 views

Do carbon film resistors have any effect on AC?

Carbon film resistors are basically an insulating (probably ceramic) rod covered in a carbon film that is twisted around it, as shown in the picture below: However, this seems very similar with a ...
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1answer
113 views

Does current change when going through a DC voltage source? [closed]

Can you get the equivalent resistance of two series resistors if there is a DC voltage source between them
0
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1answer
59 views

NE555 Timer Problem

I need help using an NE555 timer to flash an LED. Here is my current set up: All resistors are 220 Ohms and LED is link The capacitor is 10uf and same result happens with 1uf. I am using a 9V ...
0
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3answers
72 views

Maximum resistance allowing for short circuits

Consider a contrived circuit consisting of only cell and pot: (1) a cell with constant voltage V and constant amperage A, (2) variable resistor of resistance R initially set to its highest finite ...
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2answers
66 views

Best elements for downhole and high temperature circuits

I want to design a data-logger with PIC MCUs. This data-logger is going to work in chamber in the oil wells in the depth o 500 meters. and it is going to record temperature and pressure for 20 hours. ...
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3answers
81 views

What is the name of a component that combines a switch with a variable resistor?

I had some lights with a rotating switch that would turn them on/off, and then continuing to turn the switch would make them brighter. What sort of switch is this called? (it had a physical "click" to ...
8
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4answers
968 views

How can the value of a resistor be measured if it goes straight to ground?

I'm looking to integrate a LiPo charging circuit into my PCB, and found the MCP7831 IC. It's got a PROG pin, that allows you to ...
0
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2answers
144 views

Using 25 IR LEDs with Raspberry Pi and Transistor

Using a Raspberry Pi and 5V I want to use 25 IR LEDs (5mm LED, 940nm wavelength, 20 degree beam width, 100 mA continuous, 1000 mA pulse, Approx 1.6V forward voltage; ...
0
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2answers
74 views

What capacitor and resistor to use in my simple circuit?

I’m quite new to electronics but I’m making progress learning about it. I would like to make a circuit to control the speed of two electromotors. (Or two circuits to control separately, whatever is ...
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2answers
110 views

How do I deal with ideal current and voltage sources in my circuits?

Data given: electromotive force of the ideal voltage source \$E=20V\$, power output of the ideal voltage source \$P_e=3.333W\$, current of the ideal current source \$I_s=4A\$, power output of the ...
9
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1answer
1k views

Why use a 0 ohm resistor? [duplicate]

My customer's schematic uses a 0 ohm resistor for connecting analog(AGND) and digital (DGND). I think it is for testing, current measurement , fuse, jumper, test point etc but is there another ...
0
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2answers
97 views

Use battery voltage rating or fully charged voltage?

I am using a 3.7V (18650) battery, but its fully charged voltage is 3.85V. When calculating a resister for an LED circuit, do I use the battery's voltage rating (3.7V) or the fully charged voltage ...
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1answer
71 views

What is the relation between the power dissipation in resistor and the temperature rise

Which relation we use to calculate the temperature rise in resistor using the power dissipation. If we take P=R*I^2 from resistor, how much the resistor heats in this case ? I know that in ...
2
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2answers
272 views

Capacitor/resistor effect on audio signal

I have a pair of 20 years old electrostatic speakers that have an analog first order high-pass filter before the electrostatic panels, so there is a capacitor in the audio signal path. The original ...