Tagged Questions

2answers
52 views

Describe qualitatively the amount of current passing through resistor if the source oscillated at low frequency?

I am stuck on lab question 3. I do not know how to determine the current crossing the resistor for oscillating current at varying frequencies. Help is greatly appreciated
0answers
71 views

Is it possible to count human with low current?

Please look at this project http://big.dk/#projects-vvv Description says "A single person can activate the beating heart, but joining hands with others will make the heart beat even faster to create ...
2answers
67 views

Trying to visualize the wording of a question about finding the resistor that carries the highest voltage

I know how to find the higgest current in the resistor, it's just the visual that I'm second guessing. This is the question. This is the what I drew from it
3answers
111 views

Does current source affect flow of current in circuit with a variable resistor?

Suppose you have a current source in series with a resistor R the current through the R resistor would be the current generated by the current source. How would the current through the circuit change ...
5answers
184 views

Need help calculating resistance for transistor base

I have 3 12VDC/40A automotive relays (datasheet) that I want to use with my Arduino. Based on the tutorial I am following (link) I need transistor, resistor, and diode. I am not an electrical engineer ...
2answers
129 views

Will current pass without any resistance?

I've learned that a resistor converts some electrical energy into heat energy while the current flows through it and thus causes a power loss, but what if there's not any resistance in a circuit. Will ...
2answers
399 views

Detect car +12v using Arduino

I am looking to detect 12+v from a car wire using an Arduino. I have found the following schematic: I know how crazy automotive voltage can get so i just want to make sure the schematic i found ...
2answers
79 views

NCP59302 resistor question

What resistors do I need to get 5V on this chip? Sorry, I don't understand the reference to the Iadj in the formula. The section on the Iadj in Adjustable Voltage Design seems circular. ...
1answer
438 views

How to build a voltage-controlled current sink / voltage-controlled resistor

I am trying to control a current through several current-mirror device (specifically the IREF pin on the TLC5940) using a single potentiometer. I've tried using a ...
2answers
171 views

What do I need to know about leakage current?

I recently suggested a plan of removing one end of a resistor from a breadboard to remove it from the circuit in order to measure its resistance, but my mentor suggested that this won't work for high ...
1answer
95 views

Current flows from the source towards the sink

I happened upon the following schematic: simulate this circuit – Schematic created using CircuitLab It's supposed to reduce the max.voltage between the GPIO input pin and the current ...
1answer
297 views

Octopus Component Tester Analysis

I'm a beginner in electronics and my knowledge is pretty basic. I've been trying to understand how the Octopus Component Tester Works. I know that it's outputs should be used to plot a Current x ...
1answer
180 views

Calculating current in a simple circuit

I am new to electronics and am trying to figure something out: I have a source putting out 12.6V and an unknown current. I know that I can calculate current by finding the voltage drop over a ...
4answers
291 views

Is current the same coming out of an IC as it was going in?

This is my first diagram so keep that in mind. I've come up with this circuit because I've got some 74** series ICs and I want to be able to make them work. This example is a simple AND gate with ...
2answers
975 views

Do I need to use a resistor with a microswitch to limit current for an Arduino Uno?

I'm using an Arduino Uno to control a small robot and I'm starting to add micro-switches as bump-sensors. I know that when I'm creating a circuit with LEDs I need to use resistors to limit the current ...
2answers
370 views

If supply amperage is higher than max. amperage, do I need a resistor?

This is a pretty basic question, as I'm still learning the fundamentals of electronics. I understand the analogy where amperage is compared to the quantity of water moving through a hose. I have a ...
5answers
2k views

How to calculate Power Rating for Zero Ohm Resistors?

Base on my earlier question, since there supposed to be zero voltage (V=IR) drop across a 0Ω resistor, how do we select the power rating of such component? Example, let say I were to connect a zero ...
1answer
242 views

Need help designing a current controlled source in PSpice?

The image below shows an electrical network with 8 elements, a current controlled source, a bunch of resistors, one current source and a voltage source. Although I haven't labeled them, there are 5 ...
5answers
3k views

What is the usage of Zero Ohm & MiliOhm Resistor?

I am new to PCB design and I noticed that some schematics use 0Ω or 100mΩ resistors. What is their purpose and why do we need to use them in our PCB design? Normally if we wish to probe how much ...
1answer
130 views

equivalent load resistance

I have the following circuit I am having some trouble determining the relationships between Iac, Io and Iacpk. I'm not quite seeing how the final equation for Iac was determined, specifically ...
1answer
149 views

Identifying an irreducible circuit?

How would you go about identifying an irreducible circuit? By irreducible, I mean combining resistors whether in series or in parallel to reduce the circuit.
1answer
457 views

Are capacitors and inductors capable of absorbing positive power?

A resistor is capable of absorbing positive power. Why wouldn't this be true for capacitors and inductors?
2answers
546 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 ...
1answer
3k 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 ...
1answer
81 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 ...
2answers
236 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 ...
0answers
159 views

Cigarette lighter case mod [closed]

(Apologies in advance if this question is out of scope of this stackexchange but I wasn't really sure where else to post it. Any help, advice, useful links would be really appreciated though) I have ...
5answers
1k views

How can I measure the conductivity of a copper rod?

I would like to perform an experiment to measure the conductivity of a copper rod. What device can I use to perform that experiment? Is there such a thing as a conductivity meter? All I found was an ...
2answers
2k views

Why does a pull-up resistor not stop current flowing to the input pin when the switch is open?

Sorry this is such a silly question, but I can't seem to understand this. In the third diagram here it shows a pull-up resistor. I understand that when the switch S1 is closed, current is pulled ...
3answers
649 views

Simple voltage/current question about modifying a voltage-regulated adapter

I have a 7.5V, 2A, Radio Shack AC adapter and I need it to be a 7.5V, 1.5A power supply. It has one of those tip-ring style plugs on the DC end that plugs into a device to provide power. I need the ...
2answers
565 views

Single resistor powering multiple LEDs in parallel where current through resistor is lower than max allowed current for an individual LED

While writing an answer about using multiple diodes connected to a single resistor, I stumbled upon a case about which I haven't read a lot: What happens when we set the resistor so that it sets the ...
1answer
506 views

How current limiting resistor for LED affects current and voltage drops?

I'm having a bit of trouble understanding currrent limiting resistors in simple LED circuits. I know that I can determine the optimal resistor like so: $\displaystyle R=\frac{V_{s}-V_{f}}{I_{f}}$ ...
3answers
263 views

Would any current flow when batteries and resistors are set up like this?

What would the current flow be through the 1 ohm resistor? They are constant voltage sources, not batteries.
2answers
313 views

LED “Underdrive”

Is there any possible way I could've messed up this LED? I just found a bi-colored flashing LED this morning and I hooked up different voltages on it in the following order: 3.7V 3.8V 4.5V ...
2answers
197 views

Am I drawing more current if I'm giving multiple paths from supply to ground?

Illustrated as such: Am I drawing more current in the first case than the second case? Would this drain the 9V battery faster? Thanks
3answers
3k views

Whats inside a resistor?

How does a resistor "resist" current/potential? I know it's an elementary question, but I'm sure others are wondering too.
4answers
558 views

Limiting current from a 5v power supply [duplicate]

Possible Duplicate: Choosing power supply, how to get the voltage and current ratings? I have a 5V / 1A regulated supply. I'm thinking of using it to power a PCB which asks for 5V and ...
7answers
7k views

Why does a resistor need to be on the anode of an LED?

Please be kind, I am an electronics nub. This is in reference to getting an LED to emit photons. From what I read (Getting Started in Electronics - Forrest Mims III and Make: Electronics) electrons ...
4answers
378 views

Current Indicator

I want to turn an LED indicator on when current is flowing through a path. If there's no current the LED will be off, and when there's current, the LED would turn on. I've been experimenting with ...
4answers
776 views

How many resistors do I need for an 8 switch DIP switch block?

I was thinking of giving each switch it's own pull-up resistor, but this seems like it would be expensive and a little bit of overkill. But using just one pull-up for the entire block seems like it ...
3answers
623 views

Calculate Current out of Function Generator

I couldn't find an equation for this on Google/Wikipedia, but does the frequency of a function generator (we'll say that it's a sine wave) impact the current output. Example, if I had a 5 volt source ...