delabs Circuits

Saturday, April 26, 2014

Seven Segment LED display

how is the circuit for driving a seven segment led

mail from EA

A 7 segment LED display is used to display a number 0-9 using 7 LEDs, The circuit you design must have a BCD output, BCD means Binary coded decimal for number 0 it is 0000 and for number 9 it is 1001 see this chart i put in my site....  Electrical Tables

the BCD is fed to a BCD to 7 segment decoder like CD4511 or 7447 which has the logic to take care to drive your display, the displays are two types common anode and common cathode you have choose a driver to match your display, you will need to use current limiting resistors for every LED to limit current to 15mA or less. there are many circuits in my website which has examples of these.

you can also drive such displays with 7107 or 7135 to display analog signals, or with a microcontroller like 8051 using software decoding, even such examples and code is available at my website.Digital-Circuits. and Logic-Circuits.

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I made an online tutorial for seven segment LED. Hope it helps you learn more.

Digital up down BCD counter "Simple Digital up down counter CD4029, with interactive javascript simulation." You can run the circuit online and try out without wiring it up.

Digital up down BCD counter
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Saturday, April 19, 2014

Winding Transformers and Coils

i would need your help in designing transformers for rechargeable lamps. i really don't understand what the dots in front a coil stands for. all help (including pictures) would be really appreciated. my own just packed a few days ago and i would love to recoil the transformer.

mail from LA



You will have to do a lot of study in the internet, and experimentation too. Transformer winding is a specialized profession not a hobby at all. You can wind some coils or small signal transformers, that is ok. Please do not try to wind mains or 230/110 V transformers at home.

Winding Transformers

I can only give some tips, precautions and techniques to a winder. study these links....
I have put the link of a page but see all the pages of the website. The Dot polarity in a transformer stands for the direction of winding relative to each other. The Direction of winding could be clockwise or anti-clockwise.

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Sunday, April 13, 2014

NE612 - Balanced mixer with Local Oscillator

I am designing a circuit that implements an AM radio circuit that ultilises the IC Double mixer and Oscillator NE612. I was just wondering whether there is any standard symbol for this kind of IC.

mail from CM


There is no standard symbol for NE612, just a square box. You have to make a custom part in the CAD software or see if someone has done that. check these links on info of NE612 circuit and symbol....


GM47: Simple 30m Band QRP CW-Transceive 

The Rx mixer is followed by a IF stage featuring an NE592. The mixer's balanced output is directly connected to the amplifier's differential input, minimizing component count at this point.

Simple 30m Band QRP CW-Transceiver

Direct Conversion Receiver using NE612 for HF Bands

The NE612 is an integrated circuit which contains a balanced mixer with its own on-board local oscillator and voltage regulator. The mixer can provide up to 18dB of gain at 45 Mhz, and the local oscillator will operate up to 200 Mhz.

HF Transceiver using NE612

 I would be working on the Transverter first, as with this, I could try out the 9Mhz SSB Module that I already have. I would be building the Transverter for the 14 Mhz band depending on the values from my DC Receiver project using the NE612 IC
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