Semi Conductor Tester - SemTest Part 4

Testing was done in part 3, this last part is consist of following:

Final assembly

The front panel assembly can now be lowered down onto the case. Make sure that the three ribbon cables are folded neatly into the space above the lower PCB and not caught between the edges of the case or lid. Fasten the case together with four M4 screws into the corner holes, then fit the knobs to the rotary switch and the pot and the assembly is complete. 

Testing the HV crowbar

It’s now necessary to check that the HV crowbar circuit is working correctly. To do this, power up the unit, wait a few seconds and then press the Menu Select button. You will get a display like this:

Device to Test:▲

1:Diode/Zener▼

Press Enter and then the Up button. The display will then show:

Test parameter:▲

Irev(OPV)▼

Press Enter again. Set the Device Operating Voltage to 25V, using the right-hand knob. Then press the Test On/Off button to start the test.

12V-24V High-Current Motor Speed Controller Part-3

In first part we discussed about the detail of circuit, back EMF and Mosfet protection; and in second part we covered the display and menu, in this third and last part we will build and test our project. 

The DC Motor Speed Controller is built on two PC boards: a main board, and a display  board. These are joined together via a 12-way flat ribbon cable, which plugs into a pin header on the main board. 

The main board can be assembled first – see Fig.9. Start by checking the PC board for hairline cracks and for any visible shorts across the copper tracks, especially between the ground plane and any adjacent tracks. In addition, check the hole sizes for the larger hardware items by test fitting these parts into position.

Making a link
That done, begin by installing the 17 wire links. These must go in first, since some of them run underneath some components.

To straighten the link wire, first clamp one end in a vice, then stretch it slightly by pulling on the other end with a pair of pliers. It’s then just a matter of cutting the links to length and bending their leads down through 90° to match the holes in the PC board.

12-24v High Current Motor Speed Controller Part 2

In first part we discussed about the detail of circuit, back EMF and Mosfet protection; in the second part we will cover these:

Other protection measures
As already mentioned, diode D1 provides reverse polarity protection for microcontroller IC1 and the switchmode supply (IC2). Zener diode ZD1 is self-protecting in the case of reverse supply connection. However, if the supply is reversed, there will be a heavy conduction path via fast recovery diode D3 and the internal substrate diodes in the four power MOSFETs. If you are lucky, the 50A fuse will blow before the MOSFETs are damaged, but there is no  guarantee of this. SO dOn’T rEVErSE THE bATTErY cOnnEcTIOnS!

In a similar vein, if the outputs are shorted while power is applied, high current will flow  through the MOSFETs. Again, if you are lucky, the 50A fuse will blow before the MOSFETs go up in smoke. In reality, the 50A fuse is there to stop a fire! SO dOn’T SHOrT THE OUTPUTS TO THE MOTOr.

If the motor is under heavy load and becomes stalled, high currents will flow in its armature.  Depending on the motor’s rating, this may or may not blow the fuse. If the fuse  does not blow during stall conditions of the motor, the MOSFETs should survive, although they may get very hot.

12-24v High Current Motor Speed Controller Part 1

 This 12V or 24V high-current DC Motor Speed Controller is rated at up to 40A (continuous) and is suitable for heavy-duty motor applications. All control tasks are monitored by a microcontroller and as a result, the list of features is extensive.

This high-current motor speed controller is based on a PiC16F88 microcontroller. This micro provides all the fancy features, such as battery monitoring, soft-start and speed regulation. it also monitors the speed setting potentiometer and drives a 4-digit display board, which includes two pushbuttons.

The 4-digit display board is optional, but we strongly recommend that you build it, even if you only use it for the initial set-up. it unlocks the full features of the speed controller and allows all settings to be adjusted.

AVR ISP ScoketBoard

Most Atmel AVR microcontrollers can be programmed via their in-built serial programming interfaces (SPI). This method is ideal for in-situ programming, such as might be used in manufacturing or for firmware development or field upgrades.

In this scenario, the micro remains in its socket on the application board and a low-cost in-system programmer (ISP) is plugged into a dedicated programming header. In other words, the microcontroller does not have to be removed from its socket and plugged into a parallel programmer each time a firmware update is required.

However, in some cases it is desirable to programme a microcontroller stand-alone, such as when the application board is unavailable or doesn’t include an ISP (or JTAG) header. A low-cost method of stand-alone programming might also be useful where a batch of chips is needed for a small prototype run and the cost of a commercial parallel programmer is prohibitive.

Phase Angle Control Of SCR Using AT89C51

Silicon-controlled rectifiers (SCR) are solidstate semiconductor devices that are usually used in power switching circuits. SCR controls the output signal by switching it ‘on’ or ‘off,’ thereby controlling the power to the load in context. The two primary modes of SCR control are phase-angle fired—where a partial waveform is passed every half cycle—and zerocrossing fired—where a portion of the complete waveforms is passed to regulate the power.

In the phase-angle controller, the firing pulse is delayed to turn on the SCR in the middle of every half cycle. This means that every time a part of an AC cycle is cut, the power to the load also gets cut. To deliver more or less power to the load, the phase angle is increased or decreased, thereby controlling the throughput power.

There are several ways to control the firing angle of SCR. This article describes a microcontroller AT89C51-based phase-angle controller. A microcontroller can be programmed to fire SCR over the full range of half cycles—from 0 to 180°—to get a good linear relationship between the phase angle and the delivered output power.

Some of the features of this microcontroller-based phase-angle controller for SCR are:

1. Utilises the zero-crossing detector circuit

2. Controls the phase angle from 0–162°

3. Displays the phase angle on an LCD panel

4. LED indicators are used for displaying the status of SCR

5. Increases or decreases the phase angle with intervals of 18°

Basically, the zero-crossing detector circuit interrupts the microcontroller after every 10 ms. This interrupt commands the microcontroller to generate some delay (in the range of 1ms to 9 ms). The user can increase or decrease the delay in intervals of 1 ms using switches. the SCR is then fired through the opto-coupler. This repeats after every 10 ms.

Cellphone-Based Device Control With Voice Acknowledgement

Here is a circuit that lets you operate your home appliances like lights and water pump from your office or any other remote place. So if you forgot to switch off the lights or other appliances while going out, it helps you to turn off the appliance with your cellphone. Your cellphone works as the remote control for your home appliances. You can control the desired appliance by pressing the corresponding key. The system also gives you voice acknowledgement of the appliance status.

Circuit description
Fig.1 shows the circuit for cellphone based device control with voice acknowledgement. It comprises microcontroller AT89C51, DTMF decoder MT8870, voice recording/playback device APR9600 and a few discrete components.

PIC Based Air Quality Monitor

Idealy if you have a combustion heater in your home, there should be some means of monitoring the air quality. This is where the Air Quality Monitor comes in, it measures both carbon dioxide and carbon monoxide levels, and displays the results on LED bargraphs. If the concentration of either of these gases rises above a preset level, a loud alarm will sound, which means that you should turn off the heater and open the room up to fresh air.

Each bargraph comprises eight LEDs that light invidually to show eight distinct levels. In between values are displaed by lighting two adjacent LEDs. This gives a total of 15 levels that can be displayed. The four lower LEDs are green, followed by two orange and then two red LEDs. An automatic dimming circuit ensures that the LED displays are not too bright at night.

In addition, the alarm sounds if any of the top three LEDs light in either display. There are three alarm levels:

1. Main alarm sounds if the top LED lights. This consists of a 64ms-long 4kHz tone that repeats every 0.5s. 
2. Less urgent alarm sounds if the second top LED is lit (top LED off). This alarm gives a 32ms-long 4kHz ‘chip’ every four seconds (4s). 
3.   Warning alarm sounds if the third top LED is alight. This alarm mode gives a brief 16ms 4kHz ‘chirp’ every 16 seconds (16s). 

An internal fan at one end draws air through the box so that the internally mounted CO and CO2 sensors are presented with a continuous sample of the air that’s being monitored. Power for the unit comes from a 12V DC 500mA plugpack.

PICkit 2 Clone

There are many PIC programmer available, commercial and DIY devices. As Microchip introduces the new microprocessors the programming software got to be updated accordingly playing catch-up with the PIC manufacturer. That is the root of the problem with third-party PIC programmers. Microchip's PICkit 2 is the low cost ICSP programmer for Flash PICs with USB interface introduced by Microchip. Only subset of PIC microcontrollers is supported, but the list is including all the recent devices from PIC16, PIC18 and PIC24 families and certainly covers all the PICs you are most likely want to use. It is fully integrated with Microchip’s MPLAB IDE and allow not only program but debug applications as well.

PIC Based Auto Dimmer

The operation of the dimmer is based on phase control; during a full cycle of an AC waveform, a thyristor will only allow a part of the waveform to be delivered to the load. Take a look at the following waveforms:

 

The only difference is that the waveform on the left will bright the lamp higher than the waveform on the right. That is because, on the left waveform, the triac will be conductive earlier than the triac shown in the right waveform.

Serial Communication With PIC18F452

In this tutorial I will explain how to practically do a simple communication over RS232 interface. In this tutorial i ll send and receive the data using serial port, in two devices. Also you can control your home appliances using PC serial port with the help of PIC. RS232 is serial interface that means that data is transferred BIT by BIT at a time. Since data is transferred BIT by BIT so we need only a single wire two send data and an another one to receive data. One more common wire (called GND) is required between two separate circuit to enable current flow. So a total of three wire are required for communication.

Contact less IR tachometer using PIC16F628A

Tachometer is a device that gives the information about the rotational speed of any shaft or disc. It usually measures the speed in revolutions per minute (RPM). 

I want it to measure the speed of motor so for this i searched the net and found various design but unfortunately they don't worked for me, don't know why?. So i decided to make my own tachometer using PIC16F628A micro-controller and LCD.

Persistence of Vision (POV) Coding using PIC16

In this section i will tell you about the POV coding using PIC16F877A in C language. Persistence of vision is the phenomenon of the eye by which an afterimage is thought to persist for approximately one twenty-fifth of a second on the retina.

My plan is to use the fan from PC power supply; for rotating purpose. Now first of all i want to tell the two things. 1st i don't have smaller MCU that is why me using 40 pin, you can also use 28 pin if you have any. 2nd due to my hardware design fault, actually soldering fault,  i missed the RB0 pin; so to compensate it i used RD0. You can change the coding if you want for your ease.

SIRC Decoding and Appliances Control

In this tutorial i will show you how to decode the Sony SIRC protocol and control the home appliances like bulb, fan etc with the Sony remote control. Infrared remote control has been around for a very long time now. Each manufacturer use different set of protocols. For example, RC80 is used by Panasonic, RC5 is used by Philips, and SIRC is used by SONY, which is one of the simplest to decode.

Modulation is used to prevent the other light sources interference. This modulation is center around different frequencies depending on manufacturer and varies from 32KHz to 56KHz. In the case of SONY, the modulation center is 38-40KHz which means we need a IR-receiver that can receive the modulation infrared light and convert it to a TTL signal for a PIC. There are a number of IR-receivers available, each having a specific center frequency that they are more sensitive too.You can use whatever you want just remember the pin outs; i am gonna use to local IR receiver.

Electronic Combination Lock Using PIC16F628A

This electronic combination lock can be use with an outdoor gate. The functionality is implemented in software. It turns on a relay (usually to open a door) for a few seconds if someone enters the valid code. The relay can operate a power to open type electric strike with a shorting contact or a power-to-hold type electromagnetic lock with a breaking contact (we need the relay because these locks usually work with AC, not DC). The code can be changed any time after entering the current code.

Water Level Controller and motor Protector v2

This is the v2 by using PIC16F877A with minimum components. The most left circuitry is the same as in mains monitor; used to check to variation in ac voltage (operating range is between 200v ac - 240v ac). Five pull-up resistor circuitry is used to measure the water level in the desired water tank. Note that the push buttons are used here is only for illustration purpose, basically they are representing the probes (6 probes made of 28 gauge wire; one is of ground (reference) level). The left most probe indicates 20% of water in tank, next indicates 40% and so on till 100% or full level.

Mains Monitor

Mains Monitor or Manager is the circuit; i used to measure or check the ac voltage and frequency. Its accuracy is about 90-97% and quite handy for hobbyist. The ac voltage limit is 500v ac and 99Hz for frequency. There are two different ideas combine, to achieve this goal. 

Cellphone Operated Land Rover

Conventionally, wireless-controlled robots use RF circuits, which have the drawbacks of limited working range, limited frequency range and limited control. Use of a mobile phone for robotic control can overcome these limitations. It provides the advantages of robust control, working range as large as the coverage area of the service provider,no interference with other controllers and up to twelve controls.

Remote Controlled 6-Camera CCTV Switcher

Closed-circuit television (CCTV) uses video cameras to transmit signals to specific monitors. It differs from broadcast television in that the signal is not openly transmitted, though it may employ point-to-point wireless links. CCTV is often used for surveillance in areas that need security,such as banks, casinos, shops, departmental stores and airports or military installations. 
Here is a remote-controlled CCTV switcher circuit to monitor six cameras on a single or dual monitor/TV. 

Smart Voltage Stabilizer Using PIC16F877A

Voltage stabilizers are used for many appliances in homes, offices and industries. The mains supply suffers from large voltage drops due to losses on the distribution lines en route. A voltage stabilizer maintains the voltage to the appliance at the nominal value of around 220 volts even if the input mains fluctuates over a wide range.