1. MrsssSu

    Relay Pins Identify

    Hi, do the green highlighted pin to connect the main voltage and is the blue one the input switching voltage on the relay? Since there are another 2 pins near the blue highlighted pin, I assume we can connect to either pair right?
  2. MrsssSu

    Would trapping heat in a vacuum flask on hot side of Peltier be effective to cool room?

    If I trap the heat on the hot side of Peltier using a vacuum flask where no heat can escape to the surroundings so that the room can get cooled faster. Would it reduces my Peltier's efficiency and damage it? Or must I remove the heat as much as possible from the hot side to improve its efficiency?
  3. MrsssSu

    20V max DC motor, how do hairdryer work on cool air without heating filament ?

    Hi readers, Hairdryers (240V AC) actually works on a design which current passes through the heating filament (Maybe consume 220V) to produce a lot of heat whereas through the DC motor (Maybe consume 20V). I have always been curious about this Question: Hair dryer has an option of choosing the...
  4. S

    Protecting transistor from DC motor/Relay current spikes

    I setup two small circuits on breadboard with BD139 transistors to drive a 12v 0.2A motor and 24v 0.15A Relay to learn transistors, I can switch ON transistor through base resistor using 3.3v PSU. I know when motor/relay stops it can push back some current and i believe its called current...
  5. MrsssSu

    Charging circuit modifications

    Hi. above is a charging cut-off circuit. As you can see in my demo. when voltage source is 5V, the load (R9) has 5W power. When voltage drops to 4V, the load (R9) has 0 W (cut off). However, my lithium ion charging pin for my battery is 4.26V. Thus, when battery fully charged at 4.2V, the...
  6. R

    Tesla Coil Not Working. Transistor Getting Extremely Hot

    Tesla Coil Not Working. Transistor Getting Extremely Hot. See The image Below. I Did not use a switch and i did not use an led
  7. C

    Need Help Understanding Dual Transistor Flashing LED Circuit

    I am having trouble understanding how this circuit works. I've breadboarded it out and the LED flashes but I can't seem to wrap my head around how the NPN vs the PNP is creating the flash. Any help is greatly appreciated!
  8. J

    Dimmer Circuit Simulation Problem

    Hi I am trying to make a dimmer circuit with proteus. But it is not working according to our calculations. I am very new both in proteus and also learning about OP-AMPs. So I am not understanding what's wrong with the schematics. Both the current and voltage is showing zero. Here is the...
  9. cikalekli

    Thevenin's theorem BJT derivation

    Here, I want to use Thevenin with those 2 resistors in the base. How can I combine those two resistors with thevenin or do you have any other better idea to combine them? (circled with red in the picture) (PS: I don't ask the solution of the question. I'm only asking individually the...
  10. cikalekli

    Input and Output Impedance of the Common Emitter Amplifier

    Hi, I just have solved one of the bjt common emitter question below. However, I'm curious that how can I additionally find those things below: 1) Input and Output Impedance 2) AC Gain Here is the example and my hand draw solution. However, the question only asked to find Vout/Vin... Also, my...
  11. M

    Calculating dc gain of transistor

    I looked at the data sheet for tip110. According to 1 graph. The gain depends on temperature. It was a graph of collector current vs DC current gain. I saw three lines, 1 for 25 Celsius, 1 for -55 Celsius, 1 for 125 Celsius. What if the temperature is 10 Celsius, how do I calculate the gain?
  12. T

    How do I not pass current with 0V input? is it possible to change the input voltage range?

    Hello everybody! I have two questions. I have this circuit where I want to vary the input voltage (V1) between 0V and 5V to supply power to R2. Is it possible to make the circuit not supply a power (0W) to resistor R2 when my voltage V1 is 0V? When I do the simulation with 0V in V1 there is...
  13. M

    Controlling high power LED with transistor and Arduino

    Hello, I'm doing a small project and I'm stuck. I want to control brightness of 90v 185mA LED strip with my Arduino Uno. I used bd941 transistor in series with LED strip and I'm sending signal form arduino PWM digital pin to 100om resistor and then to transistor base.(in datasheets for...
  14. A

    Type 807 Tube RF amplifier with transistor a pre amp

    Hi all, I have a 807 vacuum tube and I want to make a CW RF amplifier with it. I am thinking of using transistors in pre amplifier and 807 as final power amp. I have only one tube so I cannot make push pull amp. First of all I need to know if it will be possible to make such RF amplifier. If...
  15. Selvedin

    How to make a flashing switch from a Transistor

    Hello guys, I need to make a circuit in which a transistor acts like a flashing switch. I watched some videos but the Problem is that I don't have the exact same components as in the Video shown and so my project fails. Can you help me? Kind regards to all good people
  16. Z

    Problem with transistor

    Hello, in the following image you can see a circuit with a npn transistor. I marked the given values with red and the unknown with blue. Below the circuit you can see my calculations and solutions. I'm stuck at finding I1. I would be very thankful for some guidance.
  17. J

    Having problems trying to get a high side switch to work 3V switching on 5V

    The context of my project is I am using an ESP-01 as a "smaller" circuit that is deep-sleep capable, running off a coin cell. It turns on a larger MCU with its own battery pack and runs at a higher voltage. Both work together regarding data transmission. The first time I made this thing, it was...
  18. V

    what is the smd equivalent package of BD139 NPN transistor?

    I am developing a basic switching circuit using a PIC microcontroller where the maximum drive current will be up to 2A in this case I was using BD139 but now due to my PCB has a Single-layer option I have to use SMD for it. so, please anyone suggest to me the best NPN SMD transistor for my...
  19. C

    Transistor is just not working

    Hello everybody, I have a small question about transistors. I have a npn transistor (bc337). I have 5Volts on the emitter from an arduino. The base goes to a resistor (1k) and then to ground. The collector goes to a resistor (330) and then through a LED to ground. As far as I understood the...
  20. C

    How to identify burned transistor?

    CPU Dell vostro 3668 motherboard i5 7th gen How to identify the burned transistor... 4496 is shown... Other half is missing .... Images are attached...
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