Circuits FAQ

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Saturday, August 15, 2020

Battery Boost Circuits

(This is a thread of my messenger many years ago - you will be able to notice text communication is quite difficult. sometimes even verbal expression will not specify the need, We need clear drawings and specs)

Sam: I was going thrugh some IC like MAX8880/MAX8881, can u help me with using that with input from my batteries?

dapj: let me see

Sam: It's datasheet says that Supply current [Iin] = 10uA max does it mean it will draw a max of 10uA from my battery?

dapj: it looks like it will work from 2.5 to 12V and it can give you a 5v out 200ma

Sam: Exactly!

dapj: is 5V enough 200mA too, but it cannot boost voltage

Sam: my concern is with my input. What about using rechargeable batteries [4x1, 2100mAh] to act as input to this IC. will it consume 10uA if I do so while my load to the output may vary from 100mA to 200uA

Battery Boost Circuits Max8880

dapj: if you want 5V you need to feed this atleast 5.5V this chip does not consume anything (the uA is Standby consumption )but it is not a voltage doublet or a charge pump

Sam: OK, I need to feed it anything between 5.5 -12V, Do we get recharge battery near about 2V, 2100mA

dapj - a 12 v battery can be recharged when 11.8V is reached it may charge upto 12.8 V in Li ion

Fast, smart NiCD/NiMh battery charger - The MAX713 is designed for NiCd batteries, while the 712 is for NiMh batteries.

Friday, August 14, 2020

Electronic Fifteen LED Roulette

The following was submitted on July 11th, 2007. Message: I want to combine Ne555 with 74154 IC.The indication of the outputs must be shown with LED's but up to so far it need 15 outputs ,is it possible the way i did? if not i will need your assistance

Mail from CY

LED running lights are used to decorate Christmas Trees, Festival Surroundings and even  Buildings. A Clock and a counter are basically required. Many LEDs can be used in parallel with driver transistors. Upto 15 count is is good enough. Many colors can be used and with a PWM or VCO you can make it Audio or Music effects lights like strobe lights.

Electronic Fifteen LED Roulette

Electronique RĂ©alisations - Roulette

Multi-Colored LEDs and drivers and even PIC microelectronics with Visual Effects in the form of ROM tables can make Alphabets and Numbers appear in LED arrays. Some have made Mini Ocillosocpes and Toy Spectrum Analyzers too in LED DOT Matrix Arrays.
LED Sequencer Circuit

The above circuit is another variation of a basic LED sequencer circuit. Note again the use of the 555 as a clock. The 555 is likely one of the most versatile chips ever invented. The output of the 555 is coupled to a 4017 Decade Counter Divider another very widely used chip

555 and CD4017 Running Lights
The 555 clocks 4017 counter and it counts and Ten LEDs indicate the counts. This can be used as a Sequential timer or for generating staircase waveform.


Tuesday, August 11, 2020

Noise and Hum in Audio Circuits

"I currently have a car stereo set that i use as an amplifier in my living room. but my main problem is that i a lot of noise hum when ever it is on especially when there happens to be a drop in the supply Voltage. i decided to use a voltage regulator and capacitor across (1600uF)...but it only reduced the hum a little. how can i completely eliminate the noise". - Question  by FP

Answer by delabs 

Ensure that the power supply has a full wave or bridge rectifier. If power supply transformer is say 12-0-12 two diodes must be there and a center tap ground OR If a square or round bridge is used with four leads or four diodes, then it is fine. Half wave rectification or a blown or leaky diode can cause this problem. Put all the filter caps you want and add a series choke as well the better the power supply the audio will be good.

Noise and Hum in Audio Circuits

The power supply transformer rating - voltage and current both may need to be boosted. Some very low budget transformers do not use CR-GO plates for lamination (i think it is Cold Rolled Grain Oriented ). They use plain thick metal plates without coating and hence hysteresis and eddy current both cause problems. Then you have ground loop hum and noise of semiconductors, the speaker ground and amplifier ground carry current and they should be directly connected to power supply ground, These you can understand by looking at these pages......