Hobby Projects - Insulation tester, LED Circuits, Meters.

Saturday, May 21, 2011

Step Down Capacitor - No Heat

Sometime in the eighties, I had to change a blind timer design due to non-availability of a component. A high resistance relay 600 ohm coil was not in supply, 150E was available. The Power to timer was derived from a resistor, I put a 0.47uF 630V and it Worked !. This design of mine, deriving a low voltage from a capacitor shown on right adaptation became popular. I used a 0.47uF 440V AC or 630V DC Plastic Capacitor.

Schematics of delabs: Mains Voltage Indicator

This circuit has been drawn from my memory and i have not tried it out again, just see if it is ok and then try. You should use the fuse of 100mA a slow blow if you want but it is very important. This circuit has to be enclosed in a plastic sealed enclosure to avoid contact.

Mains Voltage Indicator with a LED

Mains Voltage LED Indicator

Mains Current Indicator with a LED

You should use the fuse of 1A a slow blow if you want but it is very important. You can design the shunt R3 and Fuse rating as required by your load. Note that this circuit is to be put in series with the load like an ammeter. If you put it across the supply like a voltmeter it will fuse out or burn out. This circuit has to be enclosed in a plastic sealed enclosure to avoid contact.

Mains Current LED Indicator

Friday, May 20, 2011

Schematic to Reality a nice Perspective

Without Audiophiles and Ham-Radio enthusiasts, the field of Electronics would be Dreary and Gloomy.

From Schematic to Reality

Here is a nice page with refreshing illustrations, this page helps initiate a Electronics Newbie in the complex science of Schematic Reading.

Phantom Power and Microphone Interconnect Basics

Phantom Power and Microphone Interconnect Basics

What's that you say? You don't know your AC from your DC' Audio is considered an Alternating Current, a.k.a. "AC." (So is 120-volt "wall" power.) But electronic circuits need Direct Current (DC) to turn them on, from batteries or power supplies.

The Electric Web Matrix

DIY Pages and Know-How for those who love vacuum tubes, computers, and hearing music in its pristine form. There is an Audio and Electronics section is for the DIY computer audiophile.

My Notes - Even though i had Electronics Junk in my lab, when i was at school. (I used to call it Nuts-n-Bolts) The first project i saw being built by a friend was a Guitar Pickup using Germanium Transistors/Diodes. This was my first semiconductor schematic reading. Get into electronics now with a Audio Project, or ....

Wednesday, May 18, 2011

Alternative Energy Projects - MTM Scientific

Here are some neat projects for your study, free learning material. Solar Oven Cooker, Anemometer Circuit, Simple Data Logger.

Hand Cranked DC Generator Plans
The MTM Scientific, Inc. Experimenter Corner

Highlights are How to Measure the Power Output of Solar Panels and the Time Controlled Relay Switching Kit.

They also sell a Battery Amp Hour Meter and a Crystal Diode set which contains 1N34A diodes, 1N60 and D9B for learning electronics. They are Germanium Diodes.

An interesting Energy solution is the Hand Cranked DC Generator Plans. It describes how to build a hand operated electric power generator using a standard DC gearhead motor.

Solar Tracker Circuit Kits helps you servo position your Solar Cell Array, you can build a device which will automatically follow the sun across the sky.

Alternate Energy Plans by Lee Bell

At the PackRat WorkShop Lee Bell has archived Power-Energy Ideas, Mechanical Howto and Robot Designs too.

Alternate Energy Plans by Lee Bell

A Practical Man, His drawings are a language by itself. He has created a useful resource which will keep a DIY Enthusiast busy for many months. Alternate Energy Plans by Lee Bell

Alternate Energy, storing and managing your own small power source, are an invaluable asset for Home or Small Business.

Depending on oneself, not only develops skills but also keeps you in form always. Building an energy source cost-effectively, requires you to put in a lot of learning and building efforts.That itself may become your future Small Business

Remember Fossil Fuels are Running out fast, Only Internet Communications and Alternative Energy will keep Business Blooming.

The lifestyle has to change, The future Generations are going to face the Heat, or is it Bitter Cold ! Even Freezing ?

Coal and Steel with Steam brought about the First Industrial Boom. Then Oil created unprecedented Magic, the Second Technological Revolution. This will not last long.

If only Rover found Oil in Mars, this post was not needed.

Tuesday, May 17, 2011

Single Digit Voltmeter with LM311

I wanted to design a logic probe as a tutorial, but there were many good ones in the web so i have tried to design a single digit voltmeter. This circuit is a design, i am unable to test it now, later if i test it and find mistakes i will update this page. You can help me by pointing out the errors.
Single Digit Voltmeter with LM311
Single Digit Voltmeter with LM311

First bear it in mind that it is a single digit voltmeter which is 0-9 counts only on the positive side, that is it can measure +0 to +9V DC +/- 1V error. That may not be practical for the cost of the components above. It may be used as a toy logic probe. The reason for the circuit is not for usage, but to give design ideas. The methodology used is Gut Feel - Thumb Rule method.

First i explain the simple part, D1 a seven segment common cathode LED display is chosen as CD4511 is a sourcing driver. 4511 can be latched so it has been used here, it decodes binary 4 bit decade info to seven segment output. The four bits are derived from CD4029 up-down clock pulse counter. LM311 is a analog comparator with single supply capability which is the A-D interface.

To avoid resistors for each of the LEDs the LEDs are turned ON-OFF at 10KHz 50% duty cycle. The Nand Schmitt Trigger CD4093 is used as in IC4D as a 10KHz Clock which drives T1 transistor with a resistor R5. On turn on IC4D one input is high which is pin 12 pulled up to +5 and another Pin 13 is Low as C4 is in discharged condition in NAND gate both inputs high, gives a low output, the other combinations the output is high. So the output goes high, this starts charging the cap C4 which soon makes both inputs high, which in turn makes output low starting the discharge of C4. This is now evidently a endless loop, hence it is a oscillator. R*C = T .... 0.01uF * 10K = 100uS or 10KHz as F=1/T approx or better still multiply by 1.1 ?. I am not good at formulae but i manage with a calculator.

The supply and ground pins of CMOS chips have not been shown, see datasheet or earlier circuits.

IC4A is also a oscillator but slower which is good enough, it is slow so that a measurement can be made nearly every second. The IC4A slow clock is read by 4029 which produces a count-down binary nibble at Q1....Q4, This is converted to crude analog with R1...R4. The voltage generated is compared with the voltage you are measuring by LM311 which generates a Latch pulse to 4511 to freeze the reading where both voltages match.

Method of Operation :

IC2 is a Counter in Decade-Down mode and IC3 is a BCD to Seven Segment Decoder which Drives the Display D1. The Circuit is wired in such a way as to keep counting the Pulses from the Clock IC4A. The IC4A which is wired as Schmitt Nand Oscillator Clocks the Counter. Now to understand how this Counter and display works see this Interactive Tutorial Simple Digital Counter. For every pulse at Pin-15 of 4029 the Counter Counts down from 9-8-7-6.... and so on. But the Display is Latched by IC4C, So the Display is static even when counter is running. So while testing counter you can remove IC4C and keep LE Pin-5 of 4511 low to ground. For testing this Circuit you can use the manual clock with a pushbutton (single step) or a slow clock rate 1 Hz as in the Tutorial Simple Digital Counter.

The Transistor T1 and Oscillator IC4D is to chop the power to display at a fast rate, this avoids the adding of seven resistors. This is not required, but it saves power and reduces parts count. IC4B is is like a ON indicator, it is a spare gate.

The BCD value at output of 4029 Q1-Q4, four bits, a nibble, is converted to an analog mV value across R6. The resistors R1-R4 which are connected to Q1-Q4 have weighted resistor values for the BCD 1-2-4-8. By ohms law you can understand that the analog value across R6 is approximately proportional to the BCD value. This circuit is just a single digit A-D converter, not even as good as 4 bit converter. Which means approximate value of analog at R6 will do.

Now lastly LM311 is a Comparator, it compares the Analog BCD reference at Pin-3 and the Attenuated Input signal at Pin-2. Output Pin-7 goes high when Pin-3 voltage becomes less than Pin-2. This is made to a narrow latch pulse by C2-R12-IC4C. The latch pulse freezes the BCD data to display till the next latch pulse. R8-R9 attenuate the 0-9 V DC input to a 1/100 value. The zener Diode Z1 is for protection.

I guess the LM311 circuit should work off a single supply, but a dual supply may be required as voltage levels may be near zero. You must be able to see a staircase waveform or ramp across R6. Narrow Latch pulses at Pin-5 4511 on every ramp cycle.