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}\$)
4
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4answers
927 views
Pull Down Resistors
In my quest to understand electrical engineering, I have stubmled across this tutorial:
http://www.ladyada.net/learn/arduino/lesson5.html
I have understood the diagrams until I got to switches. I am ...
5
votes
2answers
380 views
Limiting the short circuit current of a power supply
I'm using a repurposed ATX power supply for my hobby projects since it's got 3.3/±5/±12 outputs, all of which are really convenient. But one thing I didn't really think about until I slipped my probes ...
4
votes
1answer
134 views
What are suggestions for resistor and capacitor substitutions?
When thinking about substituting components, I know that resistors are easily substituted within their 10%/5%/1% tolerances. But what about wattage on a resistor? Is it safe to do substitutions, say ...
3
votes
2answers
188 views
Understanding circuit diagram on datasheet and resistor value
I am interested in starting an intro electronics project using a IR sensor and am having a little trouble understand the application circuit given on the datasheet of the circuit. The value of ...
0
votes
3answers
263 views
How to calculate series resistor to provide a certain voltage to a pin?
I (theoretical physicist, all the basic theory, no further electrical engineering background) am just diving into Arduino and I have a very basic question:
I am playing with a Zilog ePIR motion ...
0
votes
0answers
104 views
skin and proximity effect for solid cables
I am just wondering how to compute the skin and proximity effect for solid cables. The ks and kp values in the table here:
Table
are 'just' for stranded cables etc. Thanks.
4
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3answers
303 views
Which side should I put the resistor?
I'm a beginner and trying to understand some basics of electricity.
One thing I'm having a hard time understanding is the correct side where I should put a resistor. For example, in the following ...
2
votes
4answers
325 views
Sharing a pull-up resistor
I have two IC chips. On one chip I have one 10K ohm pull-up resistor and on another chip I have three 10K ohm pull-up resistors.
At first I was using four through hole pull-up resistors. Then I ...
3
votes
2answers
472 views
Multiple resistors in series instead of using a single resistor has any advantage: heat produced by the resistors of diffent watts are different?
I have two doubts, requesting you to answer my doubts separately. :)
1) I need a resistance of 'X', so is it better to use a single resistor of 'X' value or multiple resistance of r1+r2+r3='X'?
What ...
7
votes
1answer
257 views
How to choose correct resistor with proper wattage and ohms for 6 leds connected in a serial circuit?
Let's suppose I've six LED lights with each 3.2 Volt and 20mA and all six of them are connected in one serial circuit. I know there is better setup but for this I'm using this circuit setup.
I'm ...
4
votes
2answers
175 views
how to detect variations of small resistances
I have a load cell whose resistance is varying between 318.0 and 318.8 Ohm. I have used a voltage divider but still the output voltage is rarely changing when the resistance changes.
Is there any ...
5
votes
5answers
2k views
Resistors - metal film or carbon film and what values?
I am buying a bunch of resistors as a start to my electronics hobby. These are the values I have chosen:
100, 470, 1k, 4k7, 10k, 33k, 47k, 100k, 470k, 1M
Most of my projects will involve ...
6
votes
3answers
505 views
Why would an input pin have both a pull-up and pull-down resistor?
In his answer detailing the various types of input pins, Russell McMahon leaves the following note [referring to input pins]:
there are special cases where a resistor to high and low at once is ...
4
votes
3answers
338 views
Choose the resistence with voltage divider sensor
I'm on voltage dividers circuits for reading some sensors that changes their resistance (force sentive resistor).
With my tester (with input scale set on 200K ohms) I read 23 if sensor is not touched ...
8
votes
4answers
2k views
What is the difference between burden resistor and a normal one?
I just came across the word 'Burden Resistor'. Is it any different from a normal resistor?
If it is different, where can I possibly get one? Sparkfun hasn't got one listed. Any help is ...
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vote
1answer
2k views
How to calculate current and voltage draw of a single resistor circuit?
If I have a single 270 ohm resistor connected in a circuit to a 3.3V 50mA power supply, how can I measure the voltage and current for the resistor? I'm familiar with Ohm's law V=IR, where V is the ...
1
vote
4answers
375 views
Calculating parallel resistance of a rated bulb
I have a bulb rated 110 V, 60 W and is in series with another bulb which is 110 V, 110 W. It's being powered with a 220 V source. Now, what would be the resistance of the resistor to be added in ...
0
votes
2answers
176 views
Need help with series-parallel resitor networks
If I have a parallel resistor network with different values for each resistor, how do I calculate the total resistance?
Sorry I dont have enough rep to post pics so I'll try and explain.
Lets say I ...
2
votes
2answers
271 views
Variable resistor with odd upper limit
I have a device that is controlled by connecting a resistor between two of its connectors. The resistor can take any value between 0 and X, where X is an odd value. (E.G. X=1523ohm)
Does anybody have ...
-2
votes
1answer
122 views
If apply resistor of 2K over a battery of 6v…?
If apply resistor of 2K over a battery of 6v, will I double the time that the battery can give a 3v flow of current?
4
votes
3answers
322 views
What is the difference between these resistors?
Take a look at these two different resistors:
Fig.1 source
Fig.2 source
The first one looks "normal" to me (the way resistors I've always bought in the past look..), but the second looks kind of ...
4
votes
1answer
293 views
Using a Shunt Resistor to measure current
Usually when we measure current, we have to break the circuit and place the ammeter in series.
However, if we want to make it easy to measure current at various points in a permanent circuit(for ...
3
votes
1answer
195 views
Resistor overheating
I have problem with the model of given power limiter (below are the images). Problem is in the red rounded resistor on the last image - that resistor overheats for some reason (I've put 3 ohm one ...
4
votes
1answer
607 views
How to find Emitter and Collector of an LDR
How can we find the emitter and collector of an LDR. I am using it in the following circuit but I don't know how to identify which terminal of the LDR is emitter or collector.
Here it is mentioned ...
1
vote
1answer
74 views
How do different kinds of motors behave electrically under operation?
This is sort of a follow-up to this topic: Overclocking my toothbrush
I have since measured some numbers with my DMM. Remember this is a tiny brushed DC motor in a $5 toothbrush that I am driving ...
5
votes
1answer
160 views
What's all this Voltage Coefficient stuff, Anyhow? (*)
Rocket Surgeon posted this as a comment to this question. It's from (an older copy? of) the Art of Electronics, and is about permanent (memory effect) and non permanent change in resistance over 400V ...
0
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1answer
194 views
Decrease Impedance at Higher Frequencies
I am trying to see if I understand how impedance works correctly before I build this into a real circuit. Basically I have an inductor (helmholtz coil) driven by a function generator, now by itself we ...
2
votes
1answer
124 views
Total resistance of circuit
Hi I'm struggling a bit with obtaining the total resistance of this circuit, I know it's an easy one I'm just a bit confused on how the resistors are merged using parallel and series operations, ...
3
votes
3answers
742 views
Calculating the DC voltage and current needed to obtain certain heat with a resistor
What formulas can be used to calculate how much volts and current is needed to get a resistor to heat up to a certain temperature?
I need to get a resistor (or a few next to each other - for more ...
8
votes
1answer
4k views
Do I really need resistors when controlling LEDs with Arduino?
I'm just trying out Arduino Uno for the first time with 2 blinking LEDs on a breadboard. All the tutorials on the Internet seem to use a resistor. I do know the function of resistors, but does it ...
1
vote
1answer
121 views
resistors power
I am trying to make a 10 \$\mathrm{\Omega}\$ 2 W resistor.
I was wondering if I can achieve it connecting either four parallel pairs together serially using 2.5 \$\mathrm{\Omega}\$ resistors or ...
4
votes
1answer
462 views
Difference between NE555P and 555CN?
I'm working on a circuit that uses two 555 timers. At the electronics store, they gave me a handful of 555 chips, I only noticed the difference when I finished my circuit: the R1 value is shorted out, ...
1
vote
3answers
225 views
what is the magnitude of total voltage in the below circuit?
I was working on some RLC circuits and I found a question something like this.
In series RL circuit, \$V_R\$ = 4V and \$V_L\$ = 3V. what is the magnitude of total voltage ?
I just thought \$V_T\$ = ...
5
votes
3answers
1k views
Op-Amp Input Resistor?
I'm reading through the datasheet for the TL064, which contains this figure on page 16:
This is of course an instrumentation amplifier that apparently uses an inverting amplifier's output instead ...
1
vote
3answers
155 views
Resistor before voltmeter
Let's say I take my multimeter and measure the voltage across the poles on my battery, I get some reading X volts. I then put a resistor between one terminal and the adjacent probe, this resistor has ...
1
vote
1answer
373 views
Electric circuit AC plug to DC Design Help
I'm new to designing electric circuits... but I have a simple project that I really need help on.
All I need is a AC plug source to be connected to a 100 WATT bulb and a 3V motor(motor should only ...
3
votes
2answers
281 views
Question about ICL7673 IC
I came across the ICL7673 IC used for a battery backup system but I could not understand exactly what is the role of the R2 and R4 resistors in the circuit below (marked with red):
So my question ...
0
votes
1answer
403 views
Wheatstone circuit not functioning
I have 3 dummy strain gauges suffering no strain (all 120 ohms, G.F=2.1) and the fourth (same characteristics) is meant to pick up torque at 45 degrees on a rod. It has been verified on an external ...
0
votes
2answers
402 views
Amplifying strain gauges on an arduino
I have 4 standard mild steel foil strain gauges bonded to a steel bar in a wheatstone bridge arrangement. They are implemented into a circuit with the INA 125P amplifier. I only manage to use about a ...
1
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1answer
1k views
What are the advantages and disadvantages of using signal diodes instead of resistors?
In the past to create voltage dividers or protect against back emf I have used resistors, but reading about signal diodes those situations are given as examples. I can't really comment on the inductor ...
2
votes
4answers
302 views
Could someone identify this variable resistor?
I'm trying to find this part online, to replace it, as it broke. However, using the text on the part, I wasn't able to find anything.
Could someone help me? The board itself would be 200$ to replace, ...
6
votes
2answers
250 views
Blowing resistors in parallel, in an order-controlled way
I'm supposed to make some questions, to gain some badges (just the excuse), so I'll throw one I've always been very curious about.
Imagine I want a set of resistors arranged in parallel to blow in a ...
3
votes
1answer
352 views
Can I connect ICs directly together
This is probably answered elsewhere but I can't seem to find it.
I have a circuit which uses a Mega8 to drive a couple of ICs as shown in the diagram below.
The ISP connectors in the diagram are:
...
2
votes
1answer
1k views
What is the purpose resistors and capacitor in this 555 circuit?
What is the purpose of the capacitor , the resistor , and the variable resistor ?
Do they work like clock pulses for the 555 timer?
3
votes
3answers
703 views
Compare resistance to a setpoint and trigger a relay
I want to compare a PTC thermistor to a set point, and trigger a relay if the temperature goes below a set temperature.
In particular, my temperature to turn on the relay should be 33 degrees F (845 ...
6
votes
4answers
260 views
Using resistors at their rated power
A standard 1% metal film plated-through hole (PTH) resistor is usually rated at 250 mW. Under which conditions can it handle that power? Are special mounting precautions needed, or will mounting ...
0
votes
3answers
830 views
Pull-up resistor over a microphone
What is the reason of that 1 kilo ohm connected to the microphone? Why always too high resistors are used? I couldn't find any explanation. How do we calculate these values?
2
votes
1answer
93 views
What is the point of the terminator enable pin of an RS485?
I am working on programming the logic to test an RS485 controller (reference manual here). On page 8 of the reference manual, pin A2 is described as "Terminator Enable" (TE), which enables a resistors ...
4
votes
2answers
177 views
Overheating Problem?
I have almost no electrical experience, so I apologize about the simplicity of the question in advance.
I have 4 resistors a diode and a transistor in a 22mm x 14mm x 8mm enclosure.
My concern is that ...
1
vote
2answers
183 views
Thevenin Resistance?
I don't understand our professor's explanation for the answer to this problem:
An LED is connected in series to a 150ohms pull up resistor and a MOSFET with drain-source resistance of 3ohms. The Pull ...
