Digital Volt Meter using ICL7107

                                                  

Hello Everyone!!!!!

Previously we made Digital Voltmeter using PIC16F688,but now we made the same digital voltmeter using  ICL7107.We have used ICL7107 because it displays both positive and negative voltages and the second reason to use this IC was that it is cheaper than the PIC16F688 which was used earlier and no programing is required for ICL7107.

The datasheet of ICL7107 can be downloaded by:clicking here

We wasted almost 2 week on making Digital voltmeter by taking help of  below mentioned site and then we modified the circuit and made it work.Digital Voltmeter we made is used for measuring the output voltage of your DC power supply and include 3.5-digit LED display with negative voltage indicator.This circuit should be supplied with a 5v voltage supply and consumes only around 25mA. 

You can find the link by:clicking here

Here is the modified circuit and the JPEG download of the circuit:click here

Have a look at some working snapshot of Digital Voltmeter using ICL7107.

IGBT Testing in RnD Labs

Greetings,

A few days back we had posted in our blog some pics and explanation on some High-Power devices. But never had we mentioned that we have put them in test right!!!!!

Today we have tested a High-Power IGBT in the order of 600V, 374A but we shall be utilizing only 60V,200A. Why are we using an IGBT? well, for a secret "X" project for BSNL. The tested voltage is -30V (minus thirty volts). A small picture proof and also a circuit diagram for reference is provided below.

IGBT used: GA200SA60SP (Datasheet: Click Here)

N-Channel MOSFET Testing with Analog Multimeter

The right way of testing an N-Channel MOSFET transistor is to use an Analog Multimeter. First, find out the Gate, Drain and Source from semiconductor replacement book or search its datasheet from search engine.

Once you have the cross reference or diagram for each pin of the MOSFET and your Analogue Multimeter, follow the below instructions:-

1. Set to times 10K ohm range to check it.
2.  Put the Black Probe to the Drain pin.
3.   Touch the Gate pin with the Red Probe to discharge any internal capacitance in the MOSFET.
4. Now move the Red Probe to Source pin while the Black Probe still touching the Drain pin.
5. Use your finger to touch the Gate and Drain pin together. You will notice the Analogue Multimeter pointer will move forward of the meter's scale.

 How to cross-check?

Lifting the Red Probe from the Source pin and putting it back again to the Source pin and the pointer will still remain at the middle of the meter's scale. To discharge it you have to lift the Red Probe and touch just one time on the Gate pin. This will eventually discharge the internal capacitance again.

At this time, use the Red Probe to touch on the Source pin again, the pointer would not kick at all because you have already discharge it by touching the gate pin. 

These are the good MOSFET characteristic. 

If you notice that all the result that you measured kicked towards zero ohms and will not discharge, then the FET is considered shorted and need replacement. Testing the P channel MOSFET is just the same way as when you check N channel MOSFET. What you do is to switch the probe polarity when checking the P channel. Some Analog Multimeter have the times 100k Ohm range, this type of meter can’t really test FET due to the absent of 9 Volt battery inside the Multimeter. This type of meter will not have enough power to trigger the MOSFET. Make sure you use a meter that have the times 10k ohm range selector.

Mega-High-Power Components

Greetings!!!!!!!!!!

We are burning our hands in Power Systems and with outputs in the range of 1K-Watt to 10K-Watt.

In order to work in such high powers, we have work with high Amperes and high Voltages usually in the order of hundred's simply because of the Power Law: P = VI

The main reason for this post to just share information with our readers, followers and well-wishers of the high power components used in the industry. The package of the high power components are called ISOTOP or SOT-227 package. The big black chunk of seen in the below picture is the ISOTOP of the related component. The datasheets are provided below for further information.

Below are a few pictures of the components we are using in our Power Systems.

MOSFET and IGBT - IRF5210, GA200SA60SP and IRF640

Diodes - IN4007, 1N5822 and STTH12003TV

Datasheets:

IRF5219: Click Here
IRF640: Click Here
GA200SA60SP: Click Here

1N4007: Click Here
1N5822: Click Here
STTH12003TV: Click Here
 

Dual Voltage Display (0-20v)

 Hello Everyone,

More developement on Digital Voltmeter Using PIC16F688.

 In previous voltmeter we used to measure only one voltage value.But the voltmeter is modified to diplay two voltages simutaneously.

In modified voltmeter we have assigned pin12 (RA1) as one input and pin11(RA2) as the other input to PIC16F688. The voltage to be measured is fed to one of the 8 analog channels. The reference voltage for AD conversion is chosen to be the supply voltage Vdd (+5 V).A resistor divider network is used at the input end of pin12 and pin11 to map the range of input voltage to the ADC input voltage range (0-5 V).

 Modified Program:Click here

Output

 The  DVM is tested for various input voltages ranging from 0-22 V and some snapshots of the tested DVM are given below.

 

48 Volts 60 Ampere Solar Charge Controller

Hello Everyone.......

An update to our work in Rnd Labs. A solar charge regulator or controller (as you wish), which is based on the PWM Mode built using a PIC Microcontroller. We shall see block by block explanation of the whole unit.

Here is the schematic for the whole unit:

Here is a file to download in case it is not viewable on your screen: Click Here

Let me first attack the Micro-controller based ADC and PWM units as this is the main unit which does one half of the work.

For the ADC, we are exclusively using the PIC 16F88 as it has a built in ADC converter and also its quite small in size with 18 pins. We have already covered the ADC in this post here: Follow Here

Now coming to the PWM, the PIC16F88 does have a built in PWM, but here we have to re-alter the PWM in a different way which has been explained below.

The following is some simple algorithm with pseudo-code at some places to help better understand the flow:-

; Simple 2-Stage algorithm

; Determine the hex values for 53Volts and 60 Volts

; R1 equ   53h

; R2 equ    60h

; Please note these R1, R2 values are due to scaling

; In the present case scaling is 100:5

; Determine the present Battery Voltage Say R3

10; If R3 < R1 Call Dump routine

20; If R3 >R1; If 'False go to 10”; Call PWM Routine

; Dump Routine;

; BSF Rb4; (Rb4 is the Driving output and it is set High;

; Call Delay 2sec;

; BCF Rb4; (Rb4 is set low);

; Return; Go to 10 meaning continue to check whether;

; The Battery voltage has crossed the Desired R1 Value;

; PWM Routine;

; R2-R3=R temp;

; BSF Rb4;

; DECFSZ Rtemp;

; Loop;

; BCF Rb4

; DECFSZ RTemp2; Rtemp2 + Rtemp=C (Constant);

; Loop;

; Return;

; Go to 20 

; End;

1) Effectively we determine what should be the HEX values for 53Volts (R1) and 60Volts (R2).

2) We are continuously monitoring the Battery voltage (R3)

3) If Battery is below 53 Volts we go to dump routine and make the Controller output High for 2 Seconds. Then we Make the output Low and verify the status of battery Voltage.

4) We continue with Dump stage till Battery crosses 53Volts.

5) Then we verify whether it has crossed the set value of 53 Volts and jump to PWM Routine.

6) PWM Routine: Here we check the difference between higher cutoff voltage and present voltage. The difference is ON time of PWM Off time is the inverse Meaning ON+OFF shall be same.  (On+Off gives us PRF)

7) Continuous loop from step 2

Technical Details of the Solar Charge Controller:

 

The energy coming from Solar Panel is used to charge battery using this Charge Controller.Two-Stage Controller is implemented in 16F88 Microcontroller. Charging is done in two stages: boost charge upto 53 volts and PWM method beyond 53 volts. The algorithm is provided above.

The cabinet  is all aluminum. Three sides are covered by heat sink. Chassis DOES NOT consists of any heat dissipating components.

Two diodes are used to provide reverse polarity protection for solar panel as well as battery. Each diode rating is 180 Amperes (ie, 90A*2), whereas we are pumping only 60 Amperes. The maximum dissipation is 60 Amps* diode drop which is below 150 Watts. We have provided heat sink for 200 Watt capacity each.

The MOSFET switches have resistance loss Rds=0.065 ohms.

Each MOSFET, theoretically can output 40 Amperes, whereas, we are loading only 12 Amperes. So the voltage drop is 0.78 Volts and dissipation is 9.5 Watts. Total MOSFET dissipation is 5*9.5=50 Watts as we are loading 5 MOSFET’s to share the load current. The heat sink is 500mmx100mm heat sink profile.

The selected heat sink is rated 500 Watt dissipation at Ta=25 degree centigrade.

 Finally, our unit under testing.

The complete code for the Micro-controller can be downloaded from here: 

ADC-PWM: Click Here(ASM)

ADC-PWM: Click Here(HEX)

 

Ammeter using PIC16F877

Hello Everyone,

We have made one more new experiment in RnD Labs today. This time we came up with an Ammeter using PIC16F877A. PIC16F877A is a 40pin pic microcontroller with Analog Comparator module which has two analog comparators.

The datasheet of PIC16F877A can be downloaded from this site: Click Here

 As earlier mentioned we were not satisfied with the current meter available in the market hence we made our own by taking the help of below given site.The below link mentioned is used to display both volts and currents.

You can find the link by: clicking here

For source code: click here

Whereas, in our project we are using ammeter so we modified the code to display current.

You can find the modified ammeter code by: clicking here

The current meter is tested and some snapshots of the tested current meter are shown below. 

PIC16F688 Digital Voltmeter

Hello Friends,

Today we made Digital Voltmeter using PIC16F688.  The speciality of this PIC16F688 is it is 14pin PIC and has 10bit resolution and 8 channel A/D converter

The datasheet of PIC16F688 can be downloaded from this site: click here


 So why we made this? In one of our project we have to use DVM (digital volt meter) but we were not satisfied with the digital volt meters in the market hence we constructed our own DVM by taking the help of below given site which was very easy to understand as compared to the DVM which was available in market.

 You can find the link by: clicking here


Output

 The DVM is tested for various input voltages ranging from 0-20 V and found to be very accurate. Some snapshots of the testing are here. 





 

Analog-Digital-Converter (ADC) using PIC16F88

Hello Everyone....

We have made a new progress in the RnD Labs today with a new experiment, to learn and to use in our daily electronics conquests.

We successfully completed an Analog - Digital converter using the PIC family micro-controller PIC16F88. The datasheet provided, has a very good explanation of the setup process and I promise you that it will take a good amount of time and patience to read, study, rig-up a circuit, test the circuit, write the program and then debug it and finally you will end up having a working ADC. Well all this because your doing it for the first time and hence I have provided you in this post the code that we have made/coded to get the ADC working. All the details to setup the ADC using 16F88 is below. Keep following.


The datasheet for the PIC16F88 can be found in this link: Click Here

Firstly, let us setup the circuit and test it: Here is the circuit and the JPEG download of the circuit: Click Here.

Some debugging tips for the circuit. Mainly, check the orientation of the 78L05 regulator as here you will be varying the voltage and a wrong orientation will lead to the device to fail. Also, check the potential voltage divider ratio which is why we have used a 100K and a 5K resistance in our experiment.

Now let us come to setting up the ADC and program. Below are the mentioned steps to setup the ADC in the software.

The PIC16F88 as an ADC and an Internal Oscillator which we shall be mainly using the experiment. 16F88's ADC has the following registers to be setup:

 • Analog Select Register (ANSEL) - Bank 1
• A/D Control Register 0 (ADCON0) - Bank 0
• A/D Control Register 1 (ADCON1) - Bank 1

The result of the ADC/digital output is stored in two registers based on the Right or Left justified bit. They are:

• A/D Result High Register (ADRESH) - Bank 0
• A/D Result Low Register (ADRESL) - Bank 1

 These steps should be followed for doing an A/D conversion:
1. Configure the A/D module:
            • Configure analog/digital I/O (ANSEL)
            • Configure voltage reference (ADCON1)
            • Select A/D input channel (ADCON0)
            • Select A/D conversion clock (ADCON0)
            • Turn on A/D module (ADCON0)
2. Wait the required acquisition time.
3. Start conversion:
          • Set GO/DONE bit (ADCON0)
          • Wait the required acquisition time.
4. Wait for A/D conversion to complete, by either:
          • Polling for the GO/DONE bit to be cleared
5. Read A/D Result register pair (ADRESH:ADRESL)
6. For next conversion, go to step 1 or step 2 as required.

The A/D conversion time per bit is defined as TAD. A minimum wait of 2 TAD is required before the next acquisition starts.

Although, if you still feel the above steps are little hard to follow, try to download the source code (ASM) given below which has the comments.

ADC source code : Click Here (ASM)
ADC flash file       : Click Here (HEX)
ADC full Project  :  Click Here (ZIP)

DDS New Feature: PRESET Function

Hello Everyone.

More development on the DDS and we would like to bring you a new feature in the DDS.

Ever had a passing thought that while changing frequencies during some experiments or while scanning the Rx. for stations, you would have always wondered - 'It would be great if there was a shortcut to jump to this frequency'. While that feature is termed or coined to be as Preset.

Voila, we now have a DDS with Preset feature. We have added three Preset frequency, which are set to 4.97MHz, 4.95Mhz and 4.93Mhz. Well, of course, the frequencies can be changed in the program.

Below is the modified circuit of the DDS to accommodate the Preset frequency switches:
Click Here to download the PDF.

 Downloads below:

DDSv4 ASM file: Click Here (ASM)
DDSv4 HEX file: Click Here (HEX)
DDSv4 Complete project file: Click Here (ZIP)
The DDS with Preset function was just a prototype and the PCB does not exist yet. Depending on the demand, the PCB's will be made.Also as usual, suggestions and comments are most welcomed and noted.



Stay tuned for another exciting feature to be added to DDS pretty soon!!!!