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Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.


  1. Athosworld

    Charger Noise when unplugged

    Firstly im not saying this is a problem, i just want to know what exactly causes it. When you unplug a charger its still making the transformer pitch sound but it’s instead going high and high in pitch until a buzz is heard and then the sound stops. This lasts 10 seconds. What causes it?
  2. B

    Replacing USB alimentation with batteries

    Hi all, As a homebrewer, I use some devices (iSpindel) to monitor fermentation parameters. I also have small wifi relays, DIY made by someone else, which transmit measurements to my brewing software, and also display the latest ones. These relays work very well but have a small drawback: they...
  3. hesam_m

    Double Lithium-Ion/Lithium-Polymer USB Type-C Charger

    Nowadays, Lithium batteries are used extensively in portable devices, such as cellphones, laptop computers, electronic gadgets, … etc. There is a standard industry-defined procedure (cycle) for charging the lithium-ion/lithium-polymer batteries, otherwise, the lifetime of the batteries is...
  4. P

    Self-shutoff music player with rechargeable batteries for Kids

    Hi all, I'm building a kid MP3 player with a few buttons for my 2 years old son. It's very simple: button pressed-> turn up -> play music -> auto shutoff. For my first project I selected ready-made boards (with links): LilyPad MP3: it is an arduino 3.3V with a MCP73831 3.7V Lipo charger...
  5. C

    What frequency value to use to find the correct time constant for a 22kΩ resistor?

    Hey guys, I have just been introduced to time constants and I'm having some trouble with this question. What frequency value do you plan to use to obtain the correct time constant for a 22 kΩ resistor? (Hint: It takes five time constants for a capacitor to go through the full charging...
  6. sr13579

    How to make a 5 V 1A adapter with 741 op amp?

    I am stuck with this project here. I was trying to make a voltage controlled current source which can generate 1A with 5V. I used a digaram of 741. But it didn't work. Is there anyone who can help me with showing me a circuit that can work? Thanks.
  7. mading2018

    How many filters do I need for a battery charger?

    Hello again, I have some concerns about how many EMI-filters that I should use for my AC/DC charger? My charger is operating as a low-power charing (950 W). I have read in in different articles, that some charger have only one input filter, and in some other cases they also have a output...
  8. sr13579

    How to charge my 9V battery with a no load 5V output?

    I am pretty much new with this adapter thing. I bought an adapter today with a 9 V rechargable battery. I tried my multimeter between the output and found something interesting. The output voltage is 5 volts on the 9V port. But when I am connecting the battery and turning the adapter on the...
  9. S

    Victron centaur battery charger overcharging, please help diagnose and repair

    Hi there, I have a Victron Centaur battery charger, 12v 200 amp output. It's a monster! On inspection it's actually two identical 100a chargers in the same case, connected in parallel. Other than a tiny 3 wire cable whose purpose I'm not sure of, there is nothing connecting the two chargers...
  10. sr13579

    Is it safe to use a 5V-1A USB(Samsung mobile) charger for lm386?

    Hello everyone, A brother from my hometown told me to make a mini amplifier that can pull the power out from a USB charger(or PC USB). I happened to working on a logic gate IC and burned the IC while using a USB(power bank) charger. I want to know is it safe to use a 5V-1A charger to power the...
  11. mheruian

    In-depth Battery Knowledge inquiry

    Hi, I'm new to electronics and I've been starting a project of my own which is a charger (since i though i should start first at power electronics since its all about electricity before pursuing switching electronics or automation). I had previously created a charging system (using the li-ion...
  12. EvhCo2000

    Fixing an old IBM Thinkpad charger

    Hello everyone! I'm away from home most of the day, and I'm in need of a small and sturdy laptop, so I decided to take my ol' T43 from the basement and blow that dust off. The only problem is that the charger has been "ripped" a few years now (can't remember the reason) and I'm having trouble...
  13. budget minded

    negative terminal corrosion AND now amp's distorting and cutting out with new speakers

    i have a system that consists of a 12 volt 18 amp hour battery, a planet audio BB1200.4 class D 4 channel amp, a JBL GT5-15 sub in free air, and a battery tender charger. at first, i was using proel flash 8p mini PA speakers as mains, but tonight, i hooked up a brand new pair of JBL Northridge...
  14. S

    Is this Application Report Wrong?

    I have been looking into back-flow protection for batteries and chargers and invented this wonderful circuit, and as usual when you search you find that it has all been done before. Just so in this case and the circuit in Figure #5 of the application report linked below, not only uses a similar...
  15. jourylek

    Max charging current lithuim 3s6p

    First of all let me introduce myself, I'm an electrical engineering student in college. I've been working my whole life with electronics but this is my first experience with 18650 batteries. I've made my own 50W high power flashlight and it's working nice off of wall power. However, I want to...

    Failed deWalt battery charger

    Got this charger given to me if it was worth repairing. I found both transistors shorted to zero ohms across all terminals and the resistor blown open circuit. See the hole in the yellow band. Don't know what caused it but I reckon it is a throwaway.
  17. P

    Buck converter not working as it should

    Hello everyone. I am doing a project in which I use a buck converter to convert high vtg to low vtg. Actually the input to the buck converter is from a solar panel which puts out 560 mA constant current and 34 V. And output is a 12V lead acid battery. The N- Channel mosfet is used at high side...
  18. S

    older version of CTEK MXS 5.0 lead acid charger modification help

    Hello, I have a first generation of CTEK MXS 5.0 lead acid charger. My charger does not have RECOND mode for small bateries. Differences (see attached voltage/curent tables from manuals): Questions: 1. Is there any way to limit the current to 0.3A on my charger that gives 1.5A in RECOND mode...