LCD MULTIMETER FOR YOUR SHACK MEASUREMENT U, I, P, Ah FOR GREEN ENERGY - WIND TURBINE, SOLAR PANELS MEASUREMENT U, I, P, Ah, kwh www.sp2dmb.cba.pl sp2dmb@gmail.com
MULTIMETER - ATMEGA8 Piotr Bryl SP2DMB www.sp2dmb.cba.pl sp2dmb@gmail.com Measurement: U, I, P, Ah U, I, P, Ah, kwh for Ham s shack - to wind turbine, solar panels PARAMETERS: - voltage 30V (50Vmax), resolution 0,05V - current version - current 25A, res. +/- 0,1A 3A, res. +/- 0,01A - power 750W max, res. 1W 8A, res. +/-0,02A - 999Ah, res. 0,1Ah 25A, res. +/- 0,1A - 999kWh, res. 0,1kWh - power 750W max, res. 0,1W - 99Ah, res. 0,001Ah This project is for the construction of a simple multimeter with ATMEGA8 microprocessor. In addition on the board there is a place for the temperature sensor DS18B20. PCB allows the construction of a meter to measure voltage, current, power, amp hours, kilowatt hours and the temperature. In addition, the plate pins are available that can be used to control such relays buttons. PCB is ideal for your own projects and learn programming processors! The construction is traditional THT. Dimensions: 80x50mm. The PCB is onesided, plated with solder mask and component assembly drawing.
DESCRIPTION 1 Power supply Power supply of multimeter is on the 7805 controller based (TO220) This is because of the fact that the maximum voltage supplied system, can be up to 35V. At the beginning of the track is a 1N4148 diode, which protects the system against reverse connection of power supply. The minimum supply voltage is 8V. A tile can be supplied in two ways. With an external power supply, the switch SW1 is in position 1 The second way is to capture the power supply voltage source device - the so-called. Common power. SW1 is then in position 2 For measurements below 7.5 V, use an external power supply (item 1 SW1) 2 Processor The meter uses the processor ATMEGA8-16PU. It works together with external 8MHz quartz. On the board are additional pins that are used for programming (1- RST, 7-5 V, 17-MOSI, MISO 18-19-SCK, minus the weight). Available pins are: PD0, PD1, PC5, PC4, PC3 and PC2. The reference voltage is 5V and is applied to the CPU by 100uH choke. The processor is mounted on the stand DIL28. Setting the fuse bits: CKSEL: 1111:1111, 0CKOPT: 0 3 Display Used typical LCD display 2x16 characters. This amount is sufficient to show the various types of measured values. The display device driver must be compatible with the HD44780. The diagram given for the design, configuration pins to display. Resistor R10 limits the current supplied to the display backlighting. Potentiometer P3-10k set the contrast. Before connecting the power to set the slider in the middle. After connecting to adjust in order to obtain a clear view characters. Display dimensions: 80 x 36mm. 4 Voltage measurement. Measured voltage reaches the divider R3, P2, R4. Helipot type potentiometer is used to adjust the voltage value displayed properly. For calibration, use a another digital meter. The displayed value should be the same on both gauges. To processor can not be provided a voltage higher than 5V. Therefore, in the voltage measurement circuit is diode Zener 5V1 which cuts voltage greater than this value. It follows that, we can do measurement with this resistor divider to 50V. However, in this case supply of the multimeter by switch SW1 position 2 is prohibited because to stabilizer will come in voltage greater than 35V! The measured voltage goes to the ADC input - 23 pin. 5 Current measurement Here is applied technical method, that is measurement voltage on the resistor, through which current flows. I= U/R The measurement is taken at the track ground power unit. Measuring Resistors R11 and R12 are soldered SMD and are from the paths (dotted line in the diagram assembly). The voltage drop is given by the resistor R6 to the input of operational amplifier
LM358 or MCP607. Amplification is in the range G = 6 to 15. Amplified tension goes to the ADC input processor PC1 - pin 24 6 Schematic diagram of the MULTIMETER
7 Installation diagram: * - current version 8 Connect the multimeter to the power measurement. The measured voltage and current connected from the tracks. In the picture above you will find connecting pads - dotted line (they are from the bottom). + INP - plus here is connected with the power supply. It passes through the fuse F1 to the + OUT and then to the receiver -INP - that we give less of power - it is the weight. -OUT - output minus the power supply to the receiver In the case of engine power, there may be interference with the microprocessor. 9 Temperature measurement Measurement of temperature is possible. At the bottom of the left side (see installation diagram) are goldpins to connect the sensor DS18B20. The signal should be given to the free port of the microprocessor. You can use another sensor, but you should pay attention to the correct connection of power supply and signal output. INSTALLATION NOTES Due to the low power consumption by MULTIMETER, 7805 Stabilizer does not require refrigeration.
Electrolyte C3-100uF mounted in a horizontal position. On the assembly scheme shown in broken lines potentiometer P1. If we do not have it in the version of the 3296X (the knob on the side), you can solder the 3296W version. The pins should be bend 90 degrees and mounted horizontally. Over the processor's patch. It provides a 5V voltage operational amplifier and illumination matrix. For IC is best to use the stand. This will facilitate their removal in case of damage. Display combine with a PCB with a connector HEADER 1x16 - plug + socket. In addition, we combine the four screws from the display board. In addition, we use spacers 12mm in length. The protruding screw (for display) fix another sleeve with internal threads M3 with a length of 6-8mm. The bush will allow us to install the meter to the chassis. For power, access to inputs microprocessor and sensor are used connectors type goldpin. The executed model is using car fuse. Female connectors soldered to the board. These pads + + INP and OUT. Connectors must be cut off and put a fuse. Then soldered to the board. ACCURACY OF MEASUREMENTS Accuracy is dependent on the applied processor and an operational amplifier and a resistor. PROCESSOR - like any AVR shows errors in the calculation and the writing of the program should be taken into account. When testing the finished appliance make adjustments in the program. The applied reference voltage on the meter measurement resolution imposed on us. 1024bit = 5V, which gives 0.0048 V / bit AMP - current measurement Can be successfully used the popular LM358. But we must remember that he is saddled with a large offset at the start sheet. What does that mean? If we measure the very small voltage, they will not be equally amplified. The output voltage is not adequate to set the gain. Practice shows that the linear LM358 begins work on ok.10mv at the amplifier input. So the voltage below 10mV amplified e.g 10 times do not show the correct value. Moreover, the power amplifier 5V, it can be strengthened voltage to a maximum of 3.6 V. This means that the maximum input voltage is 0.36 V. The calculations assume 3V. Non-linearity of the amplifier can be avoided in two ways. Programmatically - use if an amendment to the output voltage of the amplifier and hardware. The measurement accuracy of the block affects the final result, not only the displayed power, but the power supplied and taken ampere! Correction of hardware. Building a measure we must assume its scope. Operational amplifier works measuring resistor R11 (R12). Below is an example of how to correctly choose the desired input range span and thus maximize accuracy (resolution ADC when VREF = 5V).
Assumptions: Current measurement up to 3A. Maximum input voltage to 0.3 V amplifier (Uwyj. = 3V, G = 10) From Ohm's Law: U = R x I R = V / I is R = 0.1 ohm Power resistor is: P = R x I ^ 2 P = 0.1 x 9 = 0.9 W Heat emission affects the accuracy of measurement and we need to ensure stable operation of the resistor. For this purpose, the resistor must be used more powerful. Available in SMD are 3D and so you must use the meter. The amplifier MCP607 is an order of magnitude better performance and works well with smaller input voltages. However, you must always seek to maximize the resolution of the ADC in ATMEGA8. NOTES FOR PROGRAMMING The following listing must include a written program. It contained herein LCD control configuration used on the board: Config Lcd = 16 * 2 Config Lcdpin = Pin = Portd.5 DB4, DB5 = Portd.6, DB6 = Portd.7, Db7 = PORTB.0, E = Portd.3, Rs = PORTD.2 Video on You Tube: http://www.youtube.com/watch?v=ew20v_z7s38 ASSEMBLY INSTRUCTIONS An integral part of the meter is ATMEGA8 processor and LM358 operational amplifier. The program in the processor is configured to proper amplifier. Installation and commissioning Installation of the unit, perform the installation diagram. Before inserting the chip stand and display, connect voltage to goldpins "Plus" and "Minus". Scope of supply: 7.5-30V with respect to ground. Contacts SW1, normally are set to supply additional external. Check the voltage on leg 7 ATMEGA-i and leg 8 - operational amplifier. It should be about 5V. Disconnect voltage and load integrated circuits as terminals. Replace the display. Reconnect the tension. Potentiometer P3-10k set the contrast of the display. Connect the voltage source, which will be measured. The display will show the voltage "U". Another measure we measure the voltage source. Display on the meter to adjust the potentiometer P2 - helipot.
No-load current indication should be 0.00 A. Potentiometer P1 - helipot (under the display) to adjust the indication to that value. The exact adjustment of current measurement proceed as follows. The output meter connected in series: a light bulb and an ammeter. We make an adjustment potentiometer P2 current indications. They must be the same on LCD 2x16 and the ammeter. Top adjustment made in the mid range. For example, 3A range - Adjustable at 1.5 A, the range 8A - adjustable to 4A, etc. Due to the non-linearity of the CPU (resolution) and the amplifier display may have slight variations in readings. Precise setting voltage and current readings is essential for the indication of measuring power supplied and the number of ampere-hours taken by the receiver. Reversing the test voltage can damage the system! Use a fuse appropriate for the range! The display is mounted on the spacer sleeves. Internal threaded bushings, provide a simple way for the installation of such a power supply or charger. Ready MULTIMETER (size: 80x50x27mm) VIDEO on YouTube: http://www.youtube.com/watch?v=iqj8jljomqs&feature=em-upload_owner
For DC power supply: For wind turbine, solar panels: If You need! sp2dmb@gmail.com
Component list C1,C2,C7,C8,C9, C10,C11,C12, C13,C14 = 10 x 100n C3,C4 = 2 x 100µ C5,C6 = 2 x 33p D1 = 1 x 1N4148 D2 = 1 x 5,1V IC1 = 1 x ATMEGA8 DIL-28 = 1 x Goldpin = 11 x 1 L1 = 1 x 100µH F goldpin = 16 x 1 M goldpin = 16 x 1 LCD 16*2 HD44780= 1 x P1 helip. P2 helip. P3 trim. Q = 1 x 10k = 1 x 5k = 1 x 10K = 1 x 8MHz R2 = 1 x 6,8k R4 = 1 x 8,2k R8 = 1 x 1k R9 = 1 x 27K R10 = 1 x 510 R13 = 1 x 10k R14 = 1 x 4,7k R1,R3 = 2 x 100k R11,R12 = 2 x *see documentation R5,R6,R7 = 3 x 47k SW1 = 1 x 1 UM Goldpin = 3 x 1 T sensor1* = 1 x DS18B20 - option Goldpin = 4 x 1 U1 DIL8 = 1 x LM358, MCP607 = 1 x VR1 = 1 x 7805 Goldpin. = 2 x 1