voltage

1. Lithium ion charged at 5V 2A, why internal resistance is not 2.5 Ohms?

Lithium ion cell are charged at 5V and 2A max. Following Ohm's Law, 5V/2A would mean at least a 2.5 Ohm internal resistance of battery. However, Lithium ion internal resistance is only about 0.28 Ohms. How is that possible :)?
2. Linear voltage converter (kinda)

Good evening, I’m not an expert in electronic design by any means so please excuse any lack of understanding. I’m working on a current project where I need basically a linear voltage “adapter” I have an analog voltage DC signal of -10v to 10v and I need to somehow convert that to be between...
3. Why my Relay short-circuited ?

I have a relay but rated at 3A, 30V DC only similar to this. When I connect the Pole and NC directly using a lithium ion battery (4V), a fire occur and it shortcicruicted. However, when i measure the resistance betwwen 2 pins (Pole and NC), it reads 16 Ohms. What should i do :) ? Thank you for...
4. Can I use 5V 30 Amps PSU on a Lithium ion battery charger module?

Hi, if I use a 5V 30Amps Power Supply Unit to plug into the input of this Lithium ion battery charger module, is it fine since it will draw a limited output of 1A to charge the battery which it requires right ?
5. Battery Charging Circuit efficiency

Hi readers:), Click here . This link refers to making a lithium-ion battery charger using a BC 547. Question: How efficient is this circuit in (%) that is useful output power/ input power to charge a battery? I am planning to build a 4.2V charger but with a much higher ampere limit by...
6. High Voltage PMOS recommendation

Hi readers, is there a P-channel Mosfet with Vds of -400V but has very low Rds(On) because I want an efficient mosfet ? I a planning to power a 400V device and its negative terminal must be connected to ground (That's the reason why i use PMOS and not NMOS). I find a lot of NMOS that can...
7. Will voltage across transformer drop when charge a lithium ion battery?

If I have a 4W transformer that has high inductance, thick windings, (4V ,1 A) and converted to DC via a rectifier, in order to charge a lithium ion battery (low internal resistance) , will the output will still be slightly less than 4V or will it be very low (close to 0 which makes it...
8. Maintain constant voltage across a variable load (op-amp)

Hi readers :), Vin is fed with the PWM signal coming from an op-amp to be amplified and fed into the load R1 (1 Ohms). The purpose I design this is I want the voltage source to be a constant 5V which is independent of the load (1 Ohms or 100 Ohms). So basically, this circuit has an op-amp which...
9. How to use PMOS mosfet?

Hi readers, is this the correct way to power a PMOS mosfet? I am unfamiliar with PMOS but quite familiar with NMOS. Question: How to use PMOS to power a 10 Ohm Load? Thank you I attached LT Spice files below. Help me understand by attaching or posting a new schematic :) Thank you and have a nice...
10. Regulate voltage using op amp

Hi readers, I am doing an Op Amp voltage regulation of voltage drop across load. As you can see from diagram, I have a fluctuating_Vin (0V to 50V) and I want the voltage drop at load (100 Ohms) to be the same (14V) at all times no matter whether input voltage is 20V or 30V or 50V? Note: I...
11. Convert triangle wave to sine wave.

Hi readers, the IN node has triangular wave converted from square wave pulse. This Op-Amp acts as integrator. However, when I attach the same integrator circuit to convert this triangular wave (IN) to sine wave, the Output (OUT) I got is still quite triangular and not quite a good sine wave...
12. How do I calculate the voltage across a diode?

How do I calculate the voltage across a diode using ideal, practical, and complete models? What are the steps? I can't find any good tutorials/resources on the internet. I know the formula, but kinda confused with those many resistors. Hope someone could help
13. Amplify Flip Flop signal from NE 555 timer using transistors

Above is the graph across R7 (Load). Hi readers, Flip Flop with Ne555 timer means turning on an led and another one off, as shown in picture, and this alternate on and off pattern continues. This video can be found at Click Here . I have succeeded in amplifying one of the 2 signal as shown in...
14. PNP transistor to amplify square wave signal received at its base

Above is the load power Hi People, I created this npn transistor circuit and it works fine. So basically, it receives this square wave impulse (0 to 2V) and send it to the 10 Ohm(Load) to be amplified to become (0 to 10V). Question: How to simulate the same way (Load Power Output should be...
15. Current direction using transistors

Hi readers, I am trying to simulate current flow in both direction of the load by using 4 relays or transistors. For example, in this circuit, the load will have left current flow when 2 of the switch or transistors are on and 2 of the switch are off. The opposite way applies too if 2 of the...
16. How Power Supply Limit its Current Output ?

To view my We_bench power supply schematic Click here In the picture above, how does the power supply limit its max current and it has been fascinating for me to figure out how. Does anyone have a clue on this? I just know that the capacitor and diode help to rectify the AC output of...
17. 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?
18. 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?
19. Why transformer secondary only have 3 turns?

Here is my We Bench Design=https://webench.ti.com/power-designer/switching-regulator/customize/3?VinMin=85&VinMax=265&O1V=12&O1I=2&base_pn=UC3842A&AppType=AC&Flavor=none&op_TA=30&origin=pf_panel&lang_chosen=en-US&optfactor=3&isolated=Y&Topology=Flyback&source=AC&line_fsw=60 Question: Is it even...
20. 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...