# resistance

1. ### Human Electrical Current Circuit Touching Hands Transistor NPN

My project purpose is that when you hold hands with a friend the passage of electric current through a circuit is enough to turn a buzzer or the ISD1820 voice recorder speaker. My first idea it to use the circuit below as reference, but I have no idea which transistor I should use to have...
2. ### Changes in Multimeter reading on applying increasing contact probe pressure.

I have read different ways or reasons that could affect the measurement of multimeter readings. I am measuring resistance across a circuit at two points using a kelvin probe (Keithly 5808). I get different readings every time I take measurements of the same circuit in intervals of time. I tried...
3. ### Formula for calculating capacitor balance resistor values

$$R_{balance} = \frac{NV_{rate} - V_{bus}}{I_{maxleak}}$$ N is the number of capacitors in series Vrate is the rated maximum voltage for any one capacitor Vbus is the bus voltage (the expected voltage across the whole series of capacitors) Imaxleak is the maximum leakage current Rbalance is the...
4. ### Step-up Power Module DC-DC Boost Converter not working

I have a boost converter that i want to use to step up the voltage from 12v to 15v. (https://surplustronics.co.nz/products/7589-step-up-power-module-dc-dc-boost-converter) my power supply is 12v 12.5A, and the maximum input current is 4A. to solve this, I have a 1.5ohm resistor in parallel with...
5. ### What is electrical component is needed to reduce the output voltage from 24vac down to 6vac

Hello All, I have a wall adapter that outputs 24v AC and a small motor that requires 6v AC what resistor value is required for this voltage, please? Are resistors the same for AC as DC?
6. ### Buffer AM signal (5W)

Dear all, may I ask how to buffer an AM Signal so that it contains more power, maybe 5W for my Remote Control RC? I have buffered the AM signal using op-amp but the power output is just not enough. I have tried using this push-pull transistor pair, but the waveform seems to be unbuffered. I...
7. ### Linear Frequency to Linear Voltage circuit

Dear all, the circuit above is quoted from here, and I wish to try to produce similar graph in LT Spice but I am unsure of it. The LT Spice schematic is correct since I tested it with specific 10V input AC, and it produces linear voltage on its output. However, I want to do an AC sweep on this...
8. ### Reduce Frequency of Waveform

Dear all, may I ask if there is a circuit that produces the following input and output which basically reduces its frequency by 2 times which also basically stretch out the input waveform to produce the following output? Thank you for reading :)
9. ### Question regarding water resistance changing with voltage

Hi, recently I have been trying to find out regarding resistance of water at high voltages. I may seem oddly obsessed with this but it is forming a big part of a science project I am doing revolving around electrical safety with water and wet things, using detailed resistance values to back...
10. ### How to freeze CD 4017 (Rain Led Chip)

Dear all, I have successfully simulated a continuous led array that light up consecutively one after another using LT Spice and have even built one on breadboard and it works well. Well, my question is how would you freeze the led and how do we activate the clock inhibit on both the chips? Like...
11. ### Amplify High frequency microvolts sine wave

Dear all, I simulated a radio-receiver circuit, where I have actually build a part of the circuit which helps to amplify a sine 550kHz frequency of microvolts (antenna voltage) into several volts, however, I do not see any amplification on the output as highlighted above where I attached a...
12. ### How to buffer AM signal?

Dear all, I have actually built an AM circuit in real life to combine high frequency carrier sine wave (200kHz) and signal wave of triangle wave at (3kHz), and the output is on my oscillioscope which I am happy about. However, when I try to resonant the wave on my oscillioscope using LC tank...
13. ### AM modulation and demodulation circuit

Dear all, above shows a modulator (transmitter) and a demodulator (receiver) and the circuit works well. However, this circuit only works if the transmitter and receiver are attached by wire. What modifications should be made to transmit the wave signal wirelessly from the transmitter to...
14. ### Amplify tiny voltages accurately

Hi all, above is a Schering's Bridge as a capacitance meter. Following the equation below, Rx resistor is fixed, whereas for capacitor Cx can be placed with an unknown value capacitor. R1 will be adjusted until voltage across R4 will be 0. The problem is that the voltage fluctuation across R4...
15. ### Demodulator circuit

Below is Triangular Modulation Output of a Triangle input wave HI all, I have been trying to understand modulation and demodulation circuitry as part of my hobby :) The modulation circuit above works fine but when I connect the output of the modulator to the demodulator (as shown by blue...
16. ### TA7642 LT Spice model

Hi all, can anyone share TA7642 LT Spice model ? This IC is used in transceiver radio to demodulate the AM signal. I have tried to search the web but I could not find any of it. Datasheet is here . Thank you :)
17. ### Buffer an input signal while maintaining the same input waveform undistorted

Dear all, above shows an AM (Amplitude Modulated Signal), I was just wondering how can I make the AM waveform to have a very low impendence so that it is able to transmit high power. One solution I tried is using an op-amp as buffer which can reduce impendence while keeping the shape of waveform...
18. ### Voltage Modulation Circuit

Hi all :), I tried to simulate a modulation circuit which uses a comparator, following this click here . The output I get at the 1 kΩ resistor is weird; it should be the same shape as the send signal above. May I know what values of capacitor and inductor are used, and whether the resistor...
19. ### Increase Input Frequency circuit

Referring to website link at here , this circuit tries to replicate the waveform of input voltage and make it to a high frequency, I try to simulate the circuit in LT Spice but the output is weird. May I know the solution to this? Below is my attached LT Spice for your convenience. Thank you...
20. ### 2 way radio transmitter walkie talkie product schematic

Hi all, I am trying to search for this FLNROSE walkie talkie datasheet in the web but I couldn't find any. May I know if someone is able to find this walkie-talkie datasheet from web because I plan to get the schematic in datasheet on how this walkie-talkie works and try to desolder all...