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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27 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) ...
0
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0answers
33 views

Iphone headphones ( earpods ) [on hold]

So i cut off the headphone wire and im trying to figure out which connections of wires with wich values of resistors can i make the iphone take a picture . Please help ,it's for a project
4
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1answer
44 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 ...
-1
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0answers
56 views

I'm making a speaker with variable: Resistors, Capacitors, and Inductors. What do I need? [on hold]

I'm a total Noob at Circuits, i have no education whatsoever. But, I want to build a speaker system with the abilities of changing volume and frequency ranges. I've done a little research on the ...
0
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2answers
27 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
41 views

Power dissipation in a circuit [on hold]

What would be the power across 5ohms resistor and 3 to 7ohms (variable) resistor?Is the power same or different?why?
3
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5answers
186 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 ...
1
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1answer
32 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: ...
1
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2answers
229 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 ...
0
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0answers
36 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 ...
0
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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 ...
0
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0answers
60 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 ...
0
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2answers
76 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 ...
0
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1answer
44 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 ...
2
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2answers
63 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 ...
-4
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2answers
68 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 ...
4
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2answers
930 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 ...
0
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3answers
69 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 ...
0
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2answers
50 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 ...
0
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2answers
72 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 ...
3
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0answers
188 views

Positioning of a resistor [migrated]

Apologies in advance, my electronics knowledge is very poor. I've got myself a resistor that I believe is appropriate for the job I want to do on my vehicle. I'm replacing the factory sensor; there ...
1
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2answers
74 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 ...
0
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1answer
90 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
58 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 ...
0
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1answer
261 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
19 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
46 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 ...
0
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1answer
41 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 ...
0
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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 ...
1
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1answer
87 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 ?
0
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1answer
65 views

Schematic shows some resistor values as DNE

What does it mean on a schematic when some resistor values are listed as DNE?
8
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2answers
1k views

Why doesn't it matter if a resistor is before or behind an LED wrt voltage drop?

I have read that current is always the same within a circuit, but as far as I understood voltage is not. Every electronic part I use lowers the voltage more or less, even simple wires do this. So far, ...
3
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3answers
100 views

Are \$\frac{1}{4}\$watt 4x\$\Omega\$ Resistor and \$\frac{1}{2}\$watt x\$\Omega\$ Resistor equivalent?

We know Ohm`s law: $$\Omega = \frac{V}{I}$$ $$W=\frac{A}{t} \space\space\space\space\space\space V = \frac{A}{q} \space\space\space\space\space\space I = \frac{q}{t} \space\space\space ...
4
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1answer
165 views

Why are the resistors all different?

In my upcoming project, I am working with a Microcontroller called the Microchip PIC32MX695F512H and a Wifi Module called the Microchip MRF24WB0MA. Since I am new to electrical engineering, I've ...
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6answers
1k views

Resistors - binning and weird distributions

I read about a little quirk related to binning resistors in a comment on this recent question. Some manufacturers will sell, for example, 1% and 5% resistors that are really made in the same batch. ...
2
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2answers
154 views

Controlling 10 high power LED with a Raspberry Pi

I'm trying to figure out how to control 10 Luxeon Rebel LED (700mA) from a Raspberry Pi. I want to be able to turn them on and off from code, but I don't need to have two or more LEDs turned on at ...
0
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1answer
52 views

Simple Series Circuit: depending where the resistor is, I get different results. Explanation?

I am building a very simple Series circuit with a better (9V), two LEDs (Red, 5mm) and a resistor (220Ω). See the circuit below. Now, when I connect it all together, here is what happens: 1) (+), ...
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2answers
71 views

Beefcake relay control kit - Sparkfun

http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Components/General/RelayBoard-Large-v16.pdf I'm trying to determine the base current of the NPN transistor but keep getting numbers an order of ...
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10answers
5k views

Can a 10% resistor be used as a 1% resistor?

If my schematic calls for a 1% resistor, can I use a 10% resistor that measures to the correct resistance within 1% or is there some quality to tolerance beyond what it measures Ohm-wise? For ...
0
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0answers
30 views

Explain to me how values are read with pullup resistors [duplicate]

In the above picutre, it seems to me as if when the switch is open, a voltage of VCC is on the input pin (i.e., voltage comes in through the resistor, to the input pin then back to GND through the ...
0
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0answers
63 views

Tennis court lines, which sensor do I use to detect a ball?

I would like to make tennis court lines with a pressure/force sensor underneath them to detect when a ball is landing on them. On the internet I could only find very short pressure sensor that where ...
0
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1answer
84 views

Transistor amplifier circuits

What is the ac collector resistance for the transistor Q1? I am having trouble finding which resistors are in parallel with each other in the circuit above. I want to find the voltage gain and power ...
1
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1answer
80 views

Wired vs SMD resistor on 230V optocoupler input

For circuits similar to the one below, we used large wire resistors with proper power rating in our past designs. The question came up, if it would be a good idea to replace the resistor with SMD ...
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2answers
116 views

Fuse: why does it connect in parrallel with resistor?

I have a wire in normal condition runs 4A. The device I am using is auto-transformer, and its data sheet recommend to use fuse of 10A. So I went to buy the 10A fuse, and mount it onto a fuse holder. ...
1
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1answer
101 views

How to solve first-order RC circuit?

I've got a question, and I just keep getting myself confused when I try to solve it. The problem asks to find voltage and current and resistor currents transients (the switch is opened at t=0). ...
0
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3answers
126 views

Why does a closed circuit with a pull-up resistor output “0”?

I have a switch setup with a pull-up resistor. With the switch open I get a "1" or HIGH output and with the switch closed I get a "0" or LOW output. I understand why I am getting the "1" with it open ...
0
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2answers
79 views

Calculate resistor for red Led in series

Hello guys i am really confused about the whole resistor issue. I have visited so many sites that tells you what resistor you need but i don't know the volt drop that asks to complete or the current. ...
0
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1answer
47 views

Two-port network Current Characterization

I was trying to solve this two-pole exercise in which I had to found the z-parameters but I haven't find any clue in the textbook. How should I solve it?
3
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3answers
346 views

Control Power Resistor with MOSFET

I am making a temperature control system using an Arduino. However, I have a problem with controlling a power resistor (which is used as a heater). I was suggested to use a MOSFET to control it. ...