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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85 views

Trouble converting 12VDC incandescent to LED: lack of resistance

I'm converting two, independent, incandescent bulbs (OEM 212-2) fixtures to use LEDs for automotive map reading. Each incandescent bulb (12-volt/system) measures 1.5 ohms with a meter; however, there ...
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1answer
42 views

Resistor value calculation [duplicate]

What is the role of these two resistor please tell me that Why is first resistor 1 mega ohm the second is 100 k ? what formula has been used in this circuit to calculate first resistor and second one ...
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1answer
72 views

Heavy duty voltage resistor to decrease voltage from 120V to 100V

I have number of devices (total output 10000 Watts) that do run a bit hot when connected to 120V and are running in hot environment. Our research (using variac) have shown that dropping the voltage ...
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2answers
61 views

Resistor For Maxiumun Water Electrolysis

I've partaken in an experiment where I am looking to create the most efficient way to conduct water electrolysis. My only need is that I don't trip a breaker. I will be running at 120vac, and likely ...
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4answers
368 views

Do I need a resistor between the microcontroller and the battery? [duplicate]

I'm doing a university assignment and I need some advice. Do I need a resistor between the 9V power source and the microcontroller that uses 5.5V and 1mA? Also between a gyroscope sensor that uses 3V ...
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0answers
58 views

differential amplifier inaccuracy resistors exercise to calculate CMRR

The common mode gain for a differential amplifier in the general case is: $${V_o \over V_c }={ R_1R_4-R_2R_3 \over R_1(R_3 + R_4) }$$ simulate this circuit – Schematic created using ...
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2answers
51 views

9x 1W LED's parallel + series resistor calculation help needed

I am struggling with the calculations of the current limiting resistor for my circuit so I wanna ask you guys for help. I've tried doing this calculations on online calculators and by myself with math ...
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0answers
37 views

Vape Pen Circuit, 3 main components. Wiring/component help?

I'm looking to control a vapor pen with a variable voltage (adjustable PWM that dictates a MOSFET), followed by a SPST toggle (safety), followed by a momentary that dictates another MOSFET. The goal ...
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1answer
58 views

Voltage used up by a transistor and shift registers

i am on a project 8x8x8 LED cube and I am stuck on the value of register i should use. Talking about single layer I am using 2N5296 transistor for common cathode and 8 shift registers for controlling ...
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3answers
68 views

Current Limiter, can someone troubleshoot this circuit?

so I am trying to limit the current output with x2 3904 transistors and a sensing resistor. This is currently what I have, but am not sure why it doesn't work. That current supply is going to be a ...
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2answers
210 views

Different roles of a resistor

I graduated in Physics, then fell in love with electronics, so, in the past few months I have been trying to make heads and tails from it on my own. Today, as I was reading about amplifiers I got ...
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1answer
30 views

Switched capacitor IC

I wanted to make a switched capacitance resistance, like shown in http://en.wikipedia.org/wiki/Switched_capacitor#The_switched_capacitor_resistor. Is it possible to make such circuits on breadboards? ...
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2answers
61 views

Resistor wattage for HDMI hack

I need to add a 1K ohm resistor to a HDMI connector to solve some EDID HDMI issues. Here is the image of the person who already did that. My quesion is: Considering that voltage of pins to connect ...
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1answer
63 views

Resistor instead of flyback diode

I was looking at the data sheet of a common 12v relay and noticed it mentioned using a resistor instead of a flyback diode for circuit protection. On the last page for 12V models it reads; When ...
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2answers
341 views

Resistors with arduino

simulate this circuit – Schematic created using CircuitLab I'm using Arduino Mega Pro 5V. Pins use a max of 40-50mA. I'm connecting 3 RGB super bright 5mm LEDs. Currently wired in ...
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1answer
14 views

ADG608 multiplexer acting really strange in Multisim

I am trying to use the circuit below to switch between multiple resistors using a multiplexer. Initially I had different values of resistors attached to every channel, but since I was getting very ...
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4answers
119 views

Are these resistors in parallel

There are 2 groups of resistors that look like they might be parallel, but in between them that's making me question if they actually are. The circuit looks like this: If they are considered ...
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0answers
64 views

Voltage divider biasing circuit switch, which resistors should I use?

Goal: To turn on (open) a solenoid valve valve for irrigation when the soil moisture sensor reports a value below X% and shut it off (close) above X%. X should be able to be changed between say 20-80% ...
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1answer
48 views

LM311 Current Sensing Switch

I need to create a current sensing switch and am looking for ideas. I have very little experience with op amps / comparitors (as you'll see) but this seems to be the way to go. I am monitoring 24VDC ...
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1answer
34 views

Is this calculation for an optocoupler's resistor correct?

I'm trying to calculate what resistor to use for this optocoupler. Per the datasheet, it drops 1.3v at 50mA does this mean I should try choose a resistor that gives me 50mA? My supply is 3.3V so my ...
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3answers
68 views

Resistor/Ohm's law question?

I just used Ohm's law and I was puzzled by this. I am quite new to resistors, and I am only going to use it for an Ionocraft project to reduce the flow of current to ground. So if I have a 9v ...
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3answers
59 views

Calculate resistors value in voltage divider

I have the following voltage divider circuit with a potentiomenter, and I need to find the value of the resistors. simulate this circuit – Schematic created using CircuitLab How can I ...
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0answers
33 views

Apple headphone ( earpod) [duplicate]

I cut off the main wire of my samsung headphone and was able to make my phone snap a picture by wiring the mic wire to the ground through a 620 ( or a bit more ) ohm resistor and measured a (0.6) ...
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1answer
65 views

Recommended Layout for Parallel Current Sensing Resistors

I'm working with 12V DC systems and high currents (up to ~40A). In order to meet the wattage and price requirements for my design, I'm using two parallel sense resistors. The IC I'm using for sensing ...
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2answers
32 views

calculate value for resistor in

I have an LMC6001 op-amp, and I would like to build the ph probe amplifier featured in the datasheet. Unfortunately, I am not sure what R9 is or should be. Does R9 control slew rate? How would I ...
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2answers
42 views

Power dissipation in a circuit [closed]

What would be the power across 5ohms resistor and 3 to 7ohms (variable) resistor?Is the power same or different?why?
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5answers
209 views

How to get a variable voltage from a variable resistor

Up front, I need to declare my ignorance of electronics. I'm first and foremost a scientist/programmer, but I'm constructing a device that will allow me to control voltage to an I/O board using hand ...
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1answer
34 views

How do I decode a 5-band blue resistor [duplicate]

I found a pile of these resistors, and I didn't know how to decode them using 4-band logic. How do you know if it's to be read: ...
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2answers
240 views

How do I work out what resistor to use?

I am trying to work out what resistor to use in a circuit. The circuit is a series circuit. The power to the circuit is 5.5V, with a switch, which connects to a GPIO pin on the RasberryPi. I believe ...
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0answers
38 views

When to use Delta-Wye Transformation?

I have these two circuits needed to be simplified. Now in Case 1, is R4 and R5 in parallel connection? In that case, how does the equivalent circuit look like when R4 and R5 is simplified? Or if ...
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0answers
40 views

Calculating bias resistor with two BJTs

I'm trying to solve for R1 given the following circuit, given Vin=3.3V: Both Q1 and Q2 are ON MMBT3904L, but the datasheet specs are confusing to me. Do I assume the current through R2 is 200mA ...
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0answers
62 views

Digital Variable Resistor 0.5A

I have slider resistor with two terminals, it has 11 positions, and from my measurements, it provides this when it's running, it is DC. I want to create a digital way to control this, any ideas how ...
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2answers
78 views

Soldering multiple resistors in series

I'm starting the wiring for my project and would like to solder two resistors together in series. There is good chance that the wire will be exposed to heat and gentle turbulence. What is the best ...
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1answer
49 views

How to design a heat bed / radiator using resistors?

I have to add some resistors to an aluminium plate on a 3D printer, because it only goes to 67'C without foam insulation. The heated bed currently reads 1.6 ohms (90W at 12V) I wish to add about 96W ...
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2answers
64 views

Strange Graetz Bridge Output

Playing with electronics I discovered a strange behaviour of a Graetz bridge. This is my scheme: The corresponding output looks like this: I don't understand why I have a additional peak once a ...
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2answers
78 views

About 5 or 6 color-coding resistor ?

Beside 4 color-coding resistor we often use, I heard that there are resistors that have 5 or 6 color-coding. What's the meaning of the fifth and sixth color-coding of these kind resistor ? And which ...
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2answers
953 views

Why having two resistors (1k and 10k) in my circuit works?

I've put together a Vellman MK102 kit (Flashing LEDs) to try and get a handle on how circuit work. I wondered why resistors where placed after the LEDs, and I learned that it's because resistors ...
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3answers
77 views

How to determine watts and ohms for circuit board resistors?

I am about to embark on my first soldering job to fix a module that is broken inside my truck (compass/temperature display). It is a well known design deficiency in this particular vehicle brand as ...
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2answers
53 views

Connecting resistor in LED parallel circuit

I connect 3 LED in parallel with a two AA battery source 1.2V each. As i searched in the web i realized that it is not correct to connect them without a resistor as they may get damaged. How mane ...
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2answers
76 views

What is the purpose of the resistor on this MOSFET's drain?

Shown in the schematic below is a typical MOSFET driven by a BJT. I know the purpose of almost everything here, except for R4. I just can't figure out what the resistor on the MOSFET's drain is for Is ...
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2answers
77 views

Are my zener concepts wrong?

If a battery of 60v with internal resistnace 4kohm (in series) is connected to a zener diode of v_z=10v in parallel and a load resistance of 2kohm in parallel too, what will be the currents in ...
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1answer
107 views

Help me fix my logic circuit

I'm trying to learn more about electronics. So to do that I decided to implement boolean logic gates in a circuit simulator. So far I have made NOT, AND, NOR and a S-R latch. I wanted to try connect ...
1
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1answer
62 views

Pull down/pull up resistor for 5v input

I need to implement a pull-down resistor for a project, but I am unsure of what resistor to buy. My circuit deals with 5v inputs. Essentially, I am trying to make this: keypad scanner. Here is a ...
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1answer
524 views

Do I need a resistor when controlling an ESC with an Arduino?

I am planning to connect one of my arduino's PWM pins to the input pin of an esc and the GND pin to the GND pin of the ESC, which in conjunction with the servo library should allow me to control the ...
0
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1answer
49 views

What is the second component?

The second component on the board says Diode CKT. What is that? Doesn't the left handed side of that component look like a resistor?
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1answer
24 views

ICL 7673 circuit Hysteresis Resistor values

I'm using the ICL 7673 circuit from datasheet "without external PNP transistors". Please help with deciding Rf and Rs resistor values for 0.5V hysteresis. Any help is much appreciated. Please see ...
2
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1answer
51 views

Why is USB D+ tied to VDD (for PCM2707 at least)

I'm trying to implement an audio DAC using PCM2707 as a receiver and, looking over a couple schematics of previous implementations - at least one being verified as correct, I noticed D+ being ...
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1answer
42 views

Run multiple charging circuits on the same battery [closed]

I've recently purchased a set of 3.7V 1A Li-Ion charging circuits available HERE and was wondering if i could charge the same battery using multiples of these to get a quicker charge. Is there any ...
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2answers
47 views

Does the number of resistors make a difference?

I have got a simple circuit, where a relay is used to decide which LED lightens up (and I did a small mistake in the image: The power source is actually 12V, not 1V): simulate this circuit ...
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1answer
88 views

What are the resistors in digital pots?

Do they place tiny switches with passive resistors or are they using fets in the ohmic region ?