Panel switch wiring

Thursday, October 2, 2014

Temperature Data Logger 4 Channel Four Channel

Heres a temperature data logger circuit, an 8-pin microcontroller based circuit for temperature data logging via the serial port of any computer from between 1 and 4 remote digital temperature sensors, DS1820/DS18S20 made by Dallas.

Features of the Temperature Data Logger are are follow:

Provides realtime data via the serial port.
Interfaces up to 4 x DS1820 sensors.
Accuracy to 0.5 degrees centigrade
Fahrenheit scale selected by a jumper
No external power required
Data stream easily logged & processed.
Over 200m distance for each sensor

The sensors of temperature data logger may be located more than 200 yards from the PCB. Just check that the remote VDD is above 4.4Volts. Its recommends 10uF tantalum capacitors be placed across the power supply pins (not supplied) to minimise random errors and possibly get increased range.

Download :
- Circuit Schematic and Parts List
- Sensor Specs DS1820 DS18S20
- Software for Windows and DOS
- Source Code
- Terminal Emulator

Monday, August 25, 2014

TDA7384 4 x 22W car power amplifier

TDA7384 - 4 x 22W car power amplifier

If connect to car battery where operating voltage is about 13.2V, then each channel can give 22W(4Î©) â€“ what is more than enough for me. This amplifier I probably will use to test audio processor TDA7313 which is stil in development phase.

I didn’t find much information about this chip on the internet so I decided to built it and try on my own. As datasheets of TDA7384 says it is low distortion, low output noise, low external component count. Also has Stand-By function and Mute function. It has several protections like from output short circuit to GND or to Vs, capable to handle very inductive loads, thermal limiter, load dump voltage. TDA7384 is an AB power amplifier cased in flexiwatt25 (eagle library is included in project archive) package wich is designed for high end car radio applications. It allows rail to rail output voltage swing with no need of boot-strap capacitors.

Schematics TDA7384

I have followed the schematic in datasheed when building circuit. In datasheet you may also find PCB layout but it is two layered and didn’t fit to may box I’ve chosen. So I have made single sided PCB 50X100mm.

PCB TDA7384 amplifier

As I put pins on PCB for ST-BY and Mute but I not using them, I connected these pins to VCC like it is shown in PCB view. According to datasheet St-By and Mute turns off amplifier if signal in input is lower than 3.5V. So it is recommended to connect these pins to Vcc if not used.

Maximum power dissipation of chip is 80W(Tcase=70ÂºC), so it can handle 4 channels working at power of 20W each. But of course chip in a box doesn’t have good ventilation so I’ve put a radiator to ensure that amplifier effectively dissipates heats. I didn’t try to load amplifier to maximum to se if it doesn’t heat up to much. But at normal sound level it stays warm what is normal.

On box amplifier

Dont forget to put thermal paste between chip and radiator to ensure lower thermal resistance. And here we go â€“ brand new power amplifier ready to go:

Already to use

source: [link]

Saturday, August 23, 2014

4 watt audio amplifier circuit

I have recently included a page about AF amplifers for use with Homebrew rigs. In this I mentioned that I may include a practical one-watt circuit, complete with PCB foil and layout. Here it is, but I have taken the liberty of engineering it to provide 4-watts of AF output and with a frequency response almost suitable for Hi-Fi applications.

The circuit is very simple and incorporates darlington output transistors that will provide more than enough output current than is needed to drive a 3-ohm speaker. The gain may be pre-set for a variety of input levels, making it suitable for amplifying computer and cassette-deck Line-output levels. The input level is also suitable for use with the TDA7000 receiver. All components are easily available and I will shortly be making this project available as a kit. Naturally, the project will be built on a PCB which will also be available separately. Here is the first PCB, assembled and working.

The completed unit is 60mm x 75mm and only 30mm deep. The depth could be reduced to 10mm if the output capacitor is mounted at the speaker and the on-board electrolytics are mounted horisontally. Here are the typical performance figures that may be expected from the finished amplifer using a 3-ohm load with a 13.8-volt supply. I see no reason why the supply voltage cannot be increased a little to obtain more output power:

Parameter	Minimum	Maximum	Units
Supply voltage	8	15	volts
Output power	-	5.4	Watts
I/P for full O/P	30	4000	mV (RMS)
Noise O/P no I/P	-	0.0005	Volts RMS
Supply current (no-signal)	-	50	mA
Supply Current (Full O/P)	-	1.9	Amperes
3dB Frequency Response	42	34000	Hertz
6dB Frequency Response	21	62000	Hertz
Distortion at 2-watts	-	0.01	% (Vgain=10)

No heatsinking is required for the output transistors when running at a modest output level with either speech or music. A small heatsink should be fitted to the two TIP41 transistors if running a constant tone level. The heatsink could be bolted directly to the TIP41s without electrical isolation if the heatsinks are not going to touch anything. A heatsink with a 15-square surface area is all that is required. Here is the circuit of the amplifer.

The gain of the amplifer is set by selecting the value of the feedback resistor (Rf) on the PCB. The value of Rf is equal to 4700 / (Vgain -1) where Vgain is the voltage gain required. 4-volts RMS is the full-output level. Here is a guide for selecting the resistor.

ValueVgainTypical use
2K2 3 1300mV RMS - High levels (Small radio speaker)
470R 11 400mV RMS - e.g. computer/tape-deck Line-out
100R 48 80mV RMS - e.g. from TDA7000 RX
33R 143 30mV RMS (e.g. from microphones)

The distortion and noise levels may increase at higher gain levels, but the test board was measured with Vgain = 10 and was driving a 3-ohm car Hi-Fi speaker. With higher-impedance speakers the frequency response will become wider but the output power will reduce a little. There was no trace of instability throughout the AF range and up to 150KHz so I thought it unncecssary to include a Zobel network. Incidentally, four-watts of AF will have the wife banging on the workshop walls, so do not underestimate QRP AF!

Wednesday, August 20, 2014

6 Watt 4 Ohm Amplifier Circuit

This is an audio amplifier circuit based on IC, and IC were used that MPC563 with minimal output 6W, with impedance of 4 Ohm. Supply Voltage Minimum 4 Volt DC and a maximum voltage to 20 Volts DC. See him under this Scheme.

6 Watt 4 Ohm Amplifier Circuit

Tuesday, August 19, 2014

LCD Module in 4 bit Mode Wiring diagram Schematic

In many projects use is made of alphanumeric LCDs that are driven internally by Hitachi’s industry-standard HD44780 controller. These displays can be driven either in 4-bit or 8-bit mode. In the first case only the high nibble (D4 to D7) of the display’s data bus is used. The four unused connections still deserve some closer attention. The data lines can be used as either inputs or outputs for the display. It is well known that an unloaded output is ﬁne, but that a ﬂoating high-impedance input can cause problems. So what should you do with the four unused data lines when the display is used in 4-bit mode? This question arose when a schema was submitted to us where D0-D3 where tied directly to GND (the same applies if it was to +5 V) to stop the problem of ﬂoating inputs.

The LCD module was driven directly by a microcontroller, which was on a development board for testing various programs and I/O functions. There was a switch present for turning off the enable of the display when it wasn’t being used, but this could be forgotten during some experiments. When the R/Wline of the display is permanently tied to GND (data only goes from the microcontroller to the display) then the remaining lines can safely be connected to the supply (+ve or GND). In this application however, the R/Wline was also controlled by the microcontroller. When the display is initialised correctly then nothing much should go wrong. The data sheet for the HD44780 is not very clear as to what happens with the low nibble during initialisation.

Circuit diagram :
LCD

LCD Module in 4-bit Mode Circuit Diagram

After the power-on reset the display will always be in 8-bit mode. A simple experiment (see the accompanying schema) reveals that it is safer to use pull-down resistors to GND for the four low data lines. The data lines of the display are conﬁgured as outputs in this schema (R/Wis high) and the ‘enable’ is toggled (which can still happen, even though it is not the intention to communicate with the display). Note that in practice the RS line will also be driven by an I/O pin, and in our schema the R/W line as well. All data lines become high and it’s not certain if (and if so, for how long) the display can survive with four shorted data lines. The moral of the story is: in 4-bit mode you should always tie D0-D3 via resistors to ground or positive.

Streampowers