feedback circuit and virtual ground? Oh I think I may see. So when
the OPAMP is off, the top red LED 

current is going through the feedback
resistor (thus its “on”)to the virtual ground point? But how does it get 

switched off, when the OPAMP has an output? When the OP AMP gets an
output, I can see that going down to the green LED, but how, in that
state, does

so the ref voltage is the zener is at pin 2 (top view opamp) correct?
The 100K feedback resistor and pot are creating the hysteresis value
(meaning, the difference between pin 2 and 3 to make the opamp swing
high to its + rail voltage)? 

The op amp in this config is always trying
to make pins 2 and 3 arrive at the same value via its feedback resistor,
correct (zero, since the feedback divider is @ 0 and pin 3 is @
ground)?


Ive seen this solar charger controller done without the feed back, just
using several op amps with voltage ref pins and a pot on the other one

I dont understand the math in this circuit. Is the 100k 10k preset feedback absolutely necessary?

In other op amp circuits, they dont use any feed back just use them in
comparator config mode with ref 
 
voltage at invert/non invert pin, and
when one is exceeded, the opamp swings to its rail voltage

What is the feed back doing? I understand the opamp gain formula, in
this case is it 100k/10k x voltage difference of POT voltage
(preset)value and 4.7 zener?

or is this a Schmidt trigger type of hysteresis UTP LTP circuit

yeah I still dont get the feed back with the 100k/10k; most opamp
comparators Ive seen just use the opamp in saturation, could you explain
why the feedback and gain for this? 

Thanks
   

Please refer to the above example figure for understanding how the feedback resistor works in an Opamp circuit

I am sure you know about how voltage dividers work?
 As soon as the full

The article details a simple transistor based UPS circuit with a built-in battery charger circuit, which can be used for getting an uninterruptible mains power output cheaply, in your homes and office, shops etc. The circuit can be upgraded to any desired higher wattage level. The idea was developed by Mr. Syed Xaidi.

The following data wasprovided by Mr. Syed through email:

I saw that people are getting educated by your post. So, i think you should explain people about this schematic.
This circuit has astable mutivibrator based on transistors as you did. The capacitors c1 and c2 are the 0.47 for getting output frequency about 51.xx Hz as i measured but it is not constant in all cases.
The MOSFET has reverse high power diode that is used to charge the battery there is no need to add a special diode to the circuit. I’ve shown the switching principle with relays in the schematic. RL3 must be used with a cutt off circuit.
This circuit is very simple and i’ve tested it already. I am going to test another design of mine will share with you as soon as test is done. It controls output voltage and stabilize that using PWM. Also in that design i am using transformer 140v winding for charging and BTA16 for controlling the charging amperes. Lets hope for the Good.

​You’re doing best. Never Quit, Have a wonderful day.​
​Stay Blessed,​
—

Syed Asim Ali Xaidi
(Engineer/Musician)

Founder Of
Sam Technology Professionals
Contact : 0320-4058052

A comprehensive capacitive power supply circuit having a zero crossing detector, a surge suppressor and voltage regulator is discussed here, the idea was was submitted by Mr. Chamy

The Design

Hello Swagatam.

This is my zero crossing, surge protected capacitive power supply design with voltage stabilizer,i will try to list all of my doubts.
(I know this will be expensive for the capacitors,but this is only for testing purposes)

1-I’m not sure if the BT136 haves to be changed for a BTA06 for accommodating more current.

2-The Q1 (TIP31C) can handle only 100V Max. Maybe it should be changed for a 200V 2-3A transistor?,like the 2SC4381.

3-R6 (200R 5W),I know this resistor is pretty small and its my
fault,i actually wanted to put a 1k resistor.But with an 200R 5W
resistor it would work?

4-Some resistors have been changed following your recommendations to make it 110V capable.Maybe the 10K one needs to be smaller?

If you know how to make it work correctly,i will be very happy to correct it.If it works i can make a PCB for it and you could publish it in your page (For free of course).

Thank you for taking the time and viewing my full of faults circuit.

Have a nice day.

Chamy

My Reply:

Hello Chamy, your circuit looks OK to me.

Here are the answers to your questions:

1) yes BT136 should be replaced with a higher rated triac.

2)TIP31 should be replaced with a Darlington transistor such as TIP142 etc
otherwise it might not work properly.

3) when a Darlington is used the base resistor could be high in value, may be a 1K/2
watt resistor would be quite OK.

However the design by itself looks an overkill, a much simpler version can
be seen below

http://ift.tt/2dXFBt1

Regards
Swagatam

A cool 0-400V variable transformerless power supply circuit can be built using just a single chip LR8, and a few resistors. The IC features  a built in current control stage which makes the design extremely safe even for critical electronic circuits.

The IC LR8 is quite similar to our very own LM317 or LM338 ICs except their maximum input voltage and the current delivering capacity specs which are wide apart, rest of the attributes are exactly similar.

Since the IC LR8 is designed to work with huge voltages upto 430V, its current handling capacity is consequently much lower at 20mA maximum, but nevertheless, at 400V this current could appear significantly useful.

Since the proposed 0-400V transformerless power supply circuit is rated to work with over 400V AC, implies that this circuit could be simply plugged in with our mains socket directly without having to worry about surge inrushes, or other related catastrophic situations.

Referring to the circuit design of the 0-400V transformerless power supply above, we can see that it is exactly identical to the LM317 type voltage regulators, where R1 is used for setting up the reference voltage for the ADJ pin, while R2 is positioned for determining the intended output voltage across C2.

In the diagram the 18K resistor is supposed to produce a precise 5V at the output as long as the input voltage is 12V above the output value….meaning for acquiring 5V the minimum input supply voltage should be 17V. Similarly for ensuring a minimum 1.25V at the output, the input source will need to be around 13.2V. In short the differential voltage needs to be +12V over the desired output value.

For acquiring a smooth variable 0-400V or 0-300V DC output from a 220V mains rectified input source, the R2 could be replaced with a 100K pot.

For other fixed values the specified formula could be utilized as suggested in the diagram.

The pinout diagram for the LR8 IC can be learned from the following image:

Now since you know how to build a 0-400V transformerless power supply circuit, how do you plan to use it for your specific need?….think, and share if possible through the comment box.

The post explains a simple foot activated staircase light circuit comprising of a chain of LEDs which activate sequentially in response to each climbed step. The idea was requested by one of the dedicated members of this website.

The Request

Hi, I’m hoping you can help me. I am hoping to make a LED light up staircase.
Using LED light strips on each step I would like the circuit to be activated by a Pressure switch on the first step (and top step for coming back down). There are 2 ways I would like it to work.
Option 1:
The LED’s to light up in a delay, step-by-step with say a 1 or 2 second delay between each step illuminating. But the lights staying on until the last light is illuminated, then they all turn off together maybe 3 or 4 seconds after the last step is illuminated.
Option 2: I imagine somewhat easier and more simple would be;
The LED’s to all activate at the same time upon being activated by the pressure switch. Remaining on for 10 or 15 seconds then all turning off together.


I have not done anything like this before so would really appreciate all possible support and information.


Many thanks in advance.

The Design

The proposed foot activated staircase LED light circuit can be implemented in two unique ways:

1) The first idea allows a chain of LEDs installed across the length of the entire staircase to be lit sequentially, one after the other in response to each step climbed by the visitor.

2) The second concept allows all the LEDs to light up together when the visitors steps on the first stair, and the light is shut off as soon as the visitor has crossed the last uppermost

The first concept can be implemented by installing the following circuit across each of the stair steps:

 The piezo transducer in the design is used as a pressure to electricity converter. The piezo element is supposed to be embedded withing each of the stair, while each of the associated circuitry to be wired with it within the nearby wall along with the LED.

Once done, whenever someone steps on the staircases, the relevant piezo generates a small electric pulse in response to the vibration, which in turn triggers the 2N2222 delay OFF timer stage, and the LED which now lights up for a few seconds and then automatically shuts off.

The above action goes on happening as the visitor climbs the steps, illuminating and shutting off each subsequent LED in a sequential manner.

The second foot activated staircase light circuit idea can be enforced by installing the following across the first and the last staircases.

In the above design two piezo transducers can be seen embedded across the first and the last staircases.

When the first piezo is hit by the foot of the visitor, the tiny electrical pulses generated from the piezo is amplified by the T1/T2 stage and applied at pin#14 of the IC 4017, which is rigged as a flip flop stage here.

The trigger allows the 4017 to toggle ON the relay driver stage which lights up the LED lamp.

The process also triggers a delay ON timer circuit which begins counting the delay for which it is been fixed.

In the meantime the user continues climbing the steps until he reaches the upper most step, and his foot activates the second piezo transducer, which yet again toggles the IC 4017, but this time to switch OFF the relay driver stage and the LED.

In case the user decides not the climb the steps and returns back or takes abnormally too long to complete his journey across the steps, the delay timer comprising T3/T4 switches ON into action and resets the IC 4017 IC causing the LED to switch OFF.

If you have more innovative suggestions to improve the discussed foot activated staircase LED light circuit, please use the comment box for expressing the same.