Circuits FAQ

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Thursday, September 17, 2020

A Button and four LED Lights

Need a design - Simple one button push button to turn on 4 different LED (3mm Dome) every time you press the button. 


Attached is a circuit file that might work for you. Or make it simpler combining it with the circuit shown below.  555 Oscillator and Running Lights

A Button and four LED Lights

Make a monostable with 555 as shown here - 555 Timer based Circuits  -  and output it to a 4017 with above info, i am sure you can build or design what you want.


Temperature control for CPU

My name is IS and I am looking for somebody to design and build a simple circuit that controls a small computer fan using either a 120V plugin or a battery using a temperature switch...

In other words I would give you the set point and at that temperature it would turn on the fan and when it drops below the set point it turns off the fan.. the temperature would have to be measured using a contact type measuring device like a thermocouple or thermistor.

Mail from IS Brazil

See Craig's thermostat circuits

Try this One Chip solution from Maxim Semiconductor - MAX6641 temperature sensor and fan controller -

MAX6641 temperature sensor and fan controller

"Accurately measures the temperature of its own die and the temperature of a remote pn junction. The device reports temperature values in digital form using a 2-wire serial interface. The remote pn junction is typically the emitter-base junction of a common-collector pnp on a CPU, FPGA, or ASIC."

Some of my circuits are here Industrial Process Control Circuits


Wednesday, September 09, 2020

Motor driver H-Bridge partial

I envision a design based on the ST TD340 (page 19 of attached spec.) utilizing the power MOSFET IRF3709S (attached spec.) with external PWM-Signal (provided), separate external controller supply 20-30VDC (provided) power supply for H-Bridge up 20VDC 50A (provided) with screw-terminal type connections for control and power enclosed in a (preferably) DIN-Rail mountable enclosure that would be housed in a control cabinet (dry, 30-40C)


This part below means that you have a 20V-50A DC supply which will power this system ?

Motor driver  H-Bridge partial

"50 amp power supply with 6-18v regulator in a Board size 72mmX120mm"  separate external controller supply 20-30VDC power supply for H-Bridge up 20VDC 50A

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......

Tuesday, July 07, 2020

Microcontroller and SBC in Real World

details required for... Atmels 89C52 Microcontroller A/D D/A converter Keypad LCD display(Or LED Display) 5V Regulated power supply. Temperature & Humidity controller using PID control algorithm implemented using Atmel's 89C52 microcontroller for a AHU unit ( Analog Input from the sensor(4 wire) 0-10v dc & Output from Microcontroller is 4-20mA to the Actuator through a DAC converter).

The Temperature & Humidity to be controlled are 24±1 degree Celsius and 55%±2% Rh respectively. provide me with good LINKS.

mail from SA

Get a sensor that gives a 0-10V or 4-20mA proportional to RH% and Temp deg C. what you need to do now is to select a A/D and a D/A for a real world interface

you can visit these links.......

DigiThermo Wichit Sirichote

DigiThermo 0-100.0 °C Wichit Sirichote

Build your own a laboratory instrument for measuring time and temperature. The DigiThermo demonstrates the use of 'C' language, a dual-slope converter, LCD interfacing, and digital filtering as well..

The Assembly language program for this may be the complex, due to PID. and my uC pages micro-delabs also in my other pages you can find theory on PID etc, in them i have MCS51 code for 2 setpoint process controller.


Other uC projects sites links

Temperature and Humidity Meter -  This project is a combined temperature and humidity meter. It is an improvement on my PIC-based humidity meter and my PIC and AVR thermometers. I use an ATmega164, which as lots of I/O and memory.
    Temperature and humidity measurements with the AVR web-server- The tuxgraphics Ethernet board has a lot of general purpose IO pins where external hardware such as sensors can easily be attached. In this example we use the sensirion sht11 sensor to measure temperature, humidity and calculate the dew point.

    Working with SMD and SMT PCB

    One thing tho, i would like to request you to send me some procedures on how to work with surface mount devices (SMD's). I cant get the IC as DIP so i have no choice but improvise an SMD. What is your most professional advice on this? Is it possible you could help me with any procedures for using an SMD on a PCB circuit?.

    mail from CM

    Study These Links......... - SMD Surface Mount Device and SMT Surface Mount Technology

    you may need a big tabletop magnifier with light and a fine tip soldering iron to get started. It may be difficult and needs a lot of practice, but many people are able to do it.

    Surface-mount technology - Wiki

    Surface-mount technology - Wiki

    An SMT component is usually smaller than its through-hole counterpart because it has either smaller leads or no leads at all. It may have short pins or leads of various styles, flat contacts, a matrix of solder balls (BGAs), or terminations on the body of the component.

    Introduction to Surface Mount Technology and Surface Mount Devices

    By Dean F. Poeth, II, Ph.D., P.E., C.Mfg.E.
    For the Small Manufacturer and Hobbyist: Prototype Manufacturing, Rework, and Repair Techniques

    SMDs have improved performance over through-hole components due to their smaller size, shorter internal leads, and smaller board layouts. These factors reduce the circuit’s parasitic inductance and capacitance. SMDs can also be more cost effective than traditional through-hole components due to the smaller board size, fewer board layers, and fewer holes.

    Hints and Tips for using Surface Mount Technology (SMT) 

    What is Surface Mount Technology? Put Simply - It is a type of electronic component
    package. Most electronic components can be divided into two categories - through hole (TH)
    and surface mount (SM). Through-hole components have been used for many years and are
    designed to be loaded on one side of a printed circuit board (PCB) and soldered on the other.
    SM components are designed to be loaded and soldered on the same side of the PCB.

    Luke Enriquez. Rev 1.3. August 2001.
    VK3EM PO Box 98, Kerrimuir, Vic. 3129. Australia