16- Bit A/D converter with LCD and PIC18F2550

The analog to digital converter (ADC) is a commonly required in most of the projects. Analog voltage measurement can be done using the ADC hardware built in together in a PIC. The picture below show a simple setup for measuring the voltage through the adjustment of the potentiometer. PIC used in this example come with a 10 bit ADC. In the picture the hex value shown is the ADC value acquired from the hardware. After a simple conversion the voltage can be obtain from this value.
The next step would be to configure the register on the PIC for the ADC to operate. ADCON0 sets the refrence voltage to Vdd and Vss and select AN0 as the input for the ADC. ADCON1 configure the PIN as analog input. Only PIN AN0 is selected as analog input in this example. ADCON2 sets the required time for acquisition. The value for TAD is choose based on the calculation in the datasheet (pic18f2455, page 298-299). ADC module is turn on for it to function. To display the floating point number conversion to string must be done. The function sprintf is use to format the output so that it can be showed on the LCD. The sprintf function provided by C18 can’t be used directly on a floating point number, so the number must 1st be breakup in to the digits left and right of the decimal point. The sprintf is used to join up the 2 parts and the floating point number is display out on the 2×16 lcd. A routine for reading of ADC value is created. The acquisition is started by setting the GO bit in ADCON0. Conversion is done when the done bits turn 0. The high and low byte of the ADC results are joined in to a 16 bit data and pass back from the function. A simple formula can be use to calculate the voltage from the ADC result. The result is multiply by the max value of reference voltage and divided by 1024. Doing this will obtain the voltage on the pin AN0.

S:www.enmcu.com

reasonable performance of VGA to BNC Adapter Converter Electronic Suite

This is VGA to BNC Adapter Converter Electronic Suite. There are monitors which only have three BNC inputs and which use composite synchronization (‘sync on green’). This circuit has been designed with these types of monitor in mind. As can be seen, the circuit has been kept very simple, but it still gives a reasonable performance. The principle of operation is very straightforward. The RGB signals from the VGA connector are fed to three BNC connectors via AC-coupling capacitors. These have been added to stop any direct current from entering the VGA card. A pull-up resistor on the green output provides a DC offset, while a transistor (a BS170 MOSFET) can switch this output to ground. It is possible to get synchronisation problems when the display is extremely bright, with a maximum green component.

In this case the value of R2 should be reduced a little, but this has the side effect that the brightness noticeably decreases and the load on the graphics card increases. To keep the colour balance the same, the resistors for the other two colors (R1 en R3) have to be changed to the same value as R2. An EXOR gate from IC1 (74HC86) combines the separate V-sync and H-sync signals into a composite sync signal. Since the sync in DOS-modes is often inverted compared to the modes commonly used by Windows, the output of IC1a is inverted by IC1b. JP1 can then by used to select the correct operating mode. This jumper can be replaced by a small two-way switch, if required.

This switch should be mounted directly onto the PCB, as any connecting wires will cause a lot of interference. The PCB has been kept as compact as possible, so the circuit can be mounted in a small metal (earthed!) enclosure. With a monitor connected the current consumption will be in the region of 30 mA. A 78L05 voltage regulator provides a stable 5 V, making it possible to use any type of mains adapter, as long as it supplies at least 9 V. Diode D2 provides protection against a reverse polarity. LED D1 indicates when the supply is present. The circuit should be powered up before connecting it to an active VGA output, as otherwise the sync signals will feed the circuit via the internal protection diodes of IC1, which can be noticed by a dimly lit LED. This is something best avoided.

Resistors:

• R1,R2,R3 = 470Ω
• R4 = 100Ω
• R5 = 3kΩ3
• Capacitors:
• C1,C3,C5 = 47µF 25V radial
• C2,C4,C6,C7,C10 = 100nF ceramic
• C8 = 4µF7 63V radial
• C9 = 100µF 25V radial

Semiconductors:

• D1 = LED, high-efficiency
• D2 = 1N4002
• T1 = BS170
• IC1 = 74HC86
• IC2 = 78L05

Miscellaneous:

• JP1 = 3-way pinheader with jumper
• K1 = 15-way VGA socket (female), PCB mount (angled pins)
• K2,K3,K4 = BNC socket (female), PCB mount, 75Ω

S:electronicsuite.com

reasonable performance of VGA to BNC Adapter Converter Electronic Suite

This is VGA to BNC Adapter Converter Electronic Suite. There are monitors which only have three BNC inputs and which use composite synchronization (‘sync on green’). This circuit has been designed with these types of monitor in mind. As can be seen, the circuit has been kept very simple, but it still gives a reasonable performance. The principle of operation is very straightforward. The RGB signals from the VGA connector are fed to three BNC connectors via AC-coupling capacitors. These have been added to stop any direct current from entering the VGA card. A pull-up resistor on the green output provides a DC offset, while a transistor (a BS170 MOSFET) can switch this output to ground. It is possible to get synchronisation problems when the display is extremely bright, with a maximum green component.

In this case the value of R2 should be reduced a little, but this has the side effect that the brightness noticeably decreases and the load on the graphics card increases. To keep the colour balance the same, the resistors for the other two colors (R1 en R3) have to be changed to the same value as R2. An EXOR gate from IC1 (74HC86) combines the separate V-sync and H-sync signals into a composite sync signal. Since the sync in DOS-modes is often inverted compared to the modes commonly used by Windows, the output of IC1a is inverted by IC1b. JP1 can then by used to select the correct operating mode. This jumper can be replaced by a small two-way switch, if required.

This switch should be mounted directly onto the PCB, as any connecting wires will cause a lot of interference. The PCB has been kept as compact as possible, so the circuit can be mounted in a small metal (earthed!) enclosure. With a monitor connected the current consumption will be in the region of 30 mA. A 78L05 voltage regulator provides a stable 5 V, making it possible to use any type of mains adapter, as long as it supplies at least 9 V. Diode D2 provides protection against a reverse polarity. LED D1 indicates when the supply is present. The circuit should be powered up before connecting it to an active VGA output, as otherwise the sync signals will feed the circuit via the internal protection diodes of IC1, which can be noticed by a dimly lit LED. This is something best avoided.

Resistors:

• R1,R2,R3 = 470Ω
• R4 = 100Ω
• R5 = 3kΩ3
• Capacitors:
• C1,C3,C5 = 47µF 25V radial
• C2,C4,C6,C7,C10 = 100nF ceramic
• C8 = 4µF7 63V radial
• C9 = 100µF 25V radial

Semiconductors:

• D1 = LED, high-efficiency
• D2 = 1N4002
• T1 = BS170
• IC1 = 74HC86
• IC2 = 78L05

Miscellaneous:

• JP1 = 3-way pinheader with jumper
• K1 = 15-way VGA socket (female), PCB mount (angled pins)
• K2,K3,K4 = BNC socket (female), PCB mount, 75Ω

S:electronicsuite.com

Transformer Based 110 to 220 Converter

Transformer 220v Converter Diagram
If you want to 220V AC voltage from 110V AC source, then a 220 converter that is known as the step-up voltage converter needs to be applied for this purpose. It is very easy to do, just by using a step-up transformer.

Measuring Power Transformer Rating

In order for your 220 converter is the right choice, you need to determine wattage requirements of electronic applications that will be used to it. If your device requires 220V 1100W to work properly it needs the current 5 amperes, then the minimum current required 10 amperes at 110V input voltage.

Because of the current in the transformer is influenced by the diameter of the wire coils used in secondary and primary winding transformer. The greater the wattage you need, the greater the form of the transformer stepped up / down.

Highly recommended for a higher wattage provided for 220 converter from the load device work with it. This value can be up to 50% larger for voltage converter transformers working properly.

latest DC to DC Converter 12V to 120V

Here is a simple DC DC converter schematic using a saturation-limited to push-pull converter. DC converter can be used to power the VCR from a car battery and glow plug light aircraft models from a 12V battery starter.

As a final amplifier of the DC DC converter is a pair of transistor MJE2955 and 2SC945 as oscillator to apply sufficient bias to the final amplifier transistors.

The 2SC945 is a bias switch for startup. When applying 12V power, this transistor applies enough bias to the power transistors to get the oscillation started. Soon later, the 100uF capacitor charges up, the transistor goes off, and the power transistors self-bias into cut-off, such that cross-conduction is eliminated. After removing power, the 6k8 resistor discharges the bias timing capacitor, as otherwise the circuit would be unable to restart!

The secondary rectifiers are ultrafast diodes. These are NOT 1N4007! And the 220nF capacitors for the secondary filter are no typos; the diodes deliver almost pure DC, since the oscillation waveform is square, so only some noise filtering is needed. No electrolytics are necessary here.

DC DC Converter

Note the filters at both input and output, using ferrite cores. These are necessary to avoid polluting your environment with RF noise! Using these filters, and joining the input and output negative leads, this converter is very quiet and does not cause any problem in my combined HF, VHF and UHF station.

All ferrite cores (for the transformer and for the noise filters) are manufactured by Amidon Associates, and can be ordered directly from them in small quantities. Look for Amidon on the web. The 77-material core used for the transformer is less than ideal. A square-loop ferrite would work more efficiently! This one gets really warm, operating in saturation mode at 25 kHz. But it has worked well enough for two years now. The filter cores, on the other hand, are well chosen, so try to use the exact ones.

For all windings, the schematic states the number of turns. “7t” means 7 turns. As the transformer is quite small for the involved power, use as thick a wire as you can fit, leaving about half of the space for the 2×7 turns primary winding, and the other half for the secondary, while the feedback winding can be made from very thin wire.

The transistors do not need any heat sinks. They are large enough without, and they need to dissipate little heat!

S: circuitelectronic.net/dc-dc-converter/

DC/DC Converter From +1.5V To +34V

An interesting DC/DC converter IC is available from Linear Technology. The LT1615 step-up switching voltage regulator can generate an output voltage of up to +34V from a +1.2 to +15V supply, using only a few external components. The tiny 5-pin SOT23 package makes for very compact construction. This IC can for example be used to generate the high voltage needed for an LCD screen, the tuning voltage for a varicap diode and so on. The internal circuit diagram of the LT1615 is shown in Figure 1. It contains a monostable with a pulse time of 400 ns, which determines the off time of the transistor switch.

If the voltage sampled at the feedback input drops below the reference threshold level of 1.23 V, the transistor switches on and the current in the coil starts to increase. This builds up energy in the magnetic ?eld of the coil. When the current through the coil reaches 350 mA, the monostable is triggered and switches the transistor off for the following 400 ns. Since the energy stored in the coil must go somewhere, current continues to ?ow through the coil, but it decreases linearly. This current charges the output capacitor via the Schottky diode (SS24, 40V/2A). As long as the voltage at FB remains higher than 1.23V, nothing else happens.

As soon as it drops below this level, however, the whole cycle is repeated. The hysteresis at the FB input is 8mV. The output voltage can be calculated using the formula Vout = 1.23V (R1+R2) / R2 The value of R1 can be selected in the megohm range, since the current into the FB input is only a few tens of nano-amperes. When the supply voltage is switched on, or if the output is short-circuited, the IC enters the power-up mode. As long as the voltage at FB is less than 0.6V, the LT1615 output current is limited to 250mA instead of 350mA, and the monostable time is increased to 1.5µs.

These measures reduce the power dissipation in the coil and diode while the output voltage is rising. In order to minimize the noise voltages produced when the coil is switched, the IC must be properly decoupled by capacitors at the input and output. The series resistance of these capacitors should be as low as possible, so that they can short noise voltages to earth. They should be located as close to the IC as possible, and connected directly to the earth plane. The area of the track at the switch output (SW) should be as small as possible. Connecting a 4.7-µF capacitor across the upper feedback capacitor helps to reduce the level of the output ripple voltage.

The selection of the coil inductance is described in detail in the LT1615 data sheet at www.linear-tech.com. Normally, a 4.7µH ?lter choke is satisfactory for output voltages less than 7V. For higher voltages, a 10-µH choke should be used. In the data sheet, the Coilcraft DO1608-472 (4.7 µF) and DO1608-100 (10 µF) are recommended. The Schottky diode must naturally have a reverse blocking voltage that is significantly greater than the value of the output voltage. The types MBR0530 and SS24 are recommended. The shutdown input (/SHDN) can be used to disable the step-up regulator by applying a voltage that is less than +0.25V.

If the voltage at this pin is +0.9 V or higher, the LT1615 is active. You must bear in mind that even when the IC is disabled, the input voltage still can reach the output via the coil and the diode, reduced only by the forward voltage drop of the diode. The second circuit diagram for the LT1615 (Figure 2) shows how you can make a symmetric power supply using this switching regulator. Here the switch output of the IC is tapped off and rectified using a symmetrical rectifier. The voltage divider at the positive output of the rectifier determines the output voltage.

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RMS to DC Converter

In order to measure the RMS value of an alternating voltage an accurate converter is required to produce the true RMS value of its alternating input as a DC output. With simple sinewave inputs the RMS voltage can simply be calculated as 0.707 times the peak AC voltage, but with complex waveforms the calculation is not nearly as straightforward. The RMS value is defined as the DC voltage that would give the same heating effect in a resistor as the alternating voltage. The LTC 1966 from Linear Technology (www.linear-tech.com) uses a new form of delta-sigma conversion and is designed for battery operation, drawing only 170µA from the supply. The new technique is accurate to 0.02 % between 50 mV and 350 mV and is highly linear. It can operate from 50 Hz to 1 kHz (with an error of 0.25 %) and up to 6 kHz with a 1 % error.

The input voltage range on the differential inputs IN1 and IN2 extends to the supply rails, and so in the non-symmetrical circuit shown here the voltage on IN1 can swing between 0 V and the supply voltage. If the signal to be measured is AC only, then another coupling capacitor will be required. The input impedance is many megohms. The output voltage at the OUT pin can be offset by applying a DC voltage to the OUTRTN pin. This is particularly helpful when using the device with LCD multimeter ICs such as the 7106. A further capacitor is connected to the output which is charged up to the required voltage by the switched-capacitor circuit in the converter. The capacitor required is ten times smaller than that demanded by previous RMS to DC converter designs. The LTC1966 is not temperature sensitive and is available in an 8-pin MSOP package. It allows a tiny RMS to DC converter to be constructed using just four components.

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