Microcontroller Based Inductance Capacitance Meter

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Katrina Cox
6 years ago
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This inductance capacitance meter has Zero out switch that will reset the initial inductance capacitance, making sure that the final readings of the LC Meter are as accurate as possible.

1 Microcontroller Based Inductance Capacitance Meter MUDIT AGARWAL This is the Inductance / Capacitance Meters circuit. One can easily build this LC Meter measure inductances starting from mh to 00mH, µh to 000µH, 0nH to 000nH and capacitance from 0.pF to 0.9µF. This inductance capacitance meter has Zero out switch that will reset the initial inductance capacitance, making sure that the final readings of the LC Meter are as accurate as possible. Further this Inductance Capacitance Meter circuit uses an auto ranging system, to come over the headache to select ranges manually. The resonance frequency of LC can be determined by using the frequency formula given below. f =/(ð LC) r Note that there are three variables that we can work with; fr, L and C (fr represents a frequency, L inductance and C capacitance). If we know the values of the two variables we may calculate the value of the third variable. For example if we want to determine the value of an unknown inductor with X inductance. We plug X inductance into the formula and we also use value of a known capacitor. Using this data we can calculate the frequency. Once we know the frequency we can use the power of the algebra and rewrite the above formula to solve for L (inductance). This time we will use the calculated frequency and a value of a known capacitor to calculate the inductance. We just calculated the value of unknown inductor, and we may use the same technique to solve for the unknown capacitance and even frequency. The LC Meter uses a LM IC that functions as a frequency generator and this is exactly what we need. If we want to calculate the value of an unknown inductor we use a known000pf capacitor and the value of an unknown inductor. LM will generate a frequency that we can measure with a frequency meter. Once we have this information we can use the frequency formula to calculate the inductance. The same thing can be done for calculating the value of a unknown capacitor. This time we don't know the value a capacitor so instead we use the value of a known inductor to calculate the frequency. Once we have that information we apply the formula to determine the capacitance. All this sounds great, however if we want to determine the value of a lot of inductors / capacitors then this may become a very time consuming process. This circuit uses PIC6F84A microcontroller from microchip. PIC6F84A is like a small computer that can execute HEX programs that are written using an assembly language. PIC6F84A is a very flexible microcontroller. PIC6F84A IC requires very minimal number of external components like 4MHz crystal / resonator and few resistors depending on what project we are building. Before we can use PIC6F84A microchip we have to program it with a HEX code which has to be sent from the computer. In the next step we use the frequency generated by LM IC and pass it Pins Table. Symbol Vee Vdd Vo RS RW En D0 D D D D4 D5 D6 D7 VA VK Ground 5V Contrast Function Register Select Read Write Enable Signal Data Bit 0 Data Bit Data Bit Data Bit Data Bit 4 Data Bit 5 Data Bit 6 Data Bit 7 Backlight 5V Backlight GND

2 LCD 5 5V Pr C0 5 V DC IC Ic C C C R C8 X C9 5V 5V D D D D4 R6 K R7 R8 Transformer 0V A.C. 7 8 IC 4 C6 0uf RLY R5 6.8K R4 47K C7 0uf 00k Cknown 000pf C5 nf C4 00pf R.K Q L 8uH L LC Input Fig. : Circuit Diagram of Microcontroller Based Inductance Capacitance Meter on to PIC6F84A's PIN 7. We designate this pin as an input, as well as all other pins that are directly connected to switches and jumpers. User can use these inputs to tell the microchip to execute specified set of instructions or perform calculations. Once the microchip will calculate the unknown inductance or capacitance it will use PINs that are designated as outputs and pass the results on to the

3 6 character LCD display. Most of the character LCD displays have 4 or 6 PINs. LCD with 4 pins donot have backlight. The LCD pins function is shown in table. Software J JJ config _hs_osc & _wdt_off & _pwrte_on & _cp_off list p=pic6f84a include p6f84a.inc J9 J0 c0m equ h'0c' c0m equ h'0d' c0s equ h'0e' IC c0s equ h'0f' lcd7_0 equ b'0000' lcd7_ equ b'00000' lcd7_ equ b'00000' L R lcd7_ equ b'00000' R5 R lcd7_4 equ b'000000' Sw lcd7_5 equ b'000000' R7 lcd7_6 equ b'0000' lcd7_7 equ b' ' R8 RLY lcd7_8 equ b'0000' R6 Ic R4 Q LC Input lcd7_9 equ b' ' C7 lcd70 equ h'0' lcd7 equ h'' C6 Cknown C5 C4 lcd7 equ h'' lcd7 equ h'' lcd74 equ h'4' D D C lcd75 equ h'5' v AC D D4 C lcd76 equ h'6' C Ic lcd77 equ h'7' lcd78 equ h'8' Fig.: Component Layout o Microcontroller Based Inductance Capacitance Meter. SEMICONDUCTOR DEVICES IC 7805 IC PIC6f84A Ic LM D-D4 N4007 CAPACITORS C 000uf/5V C,C,C0 0.uf C8,C9 pf C4 00pf C5 nf C6,C7 0uf Cknown 000pf RESISTORS R 0K R.K R4 47K R5 6.8K R6 K R7,R8 Pr K COMPONENT LIST MISCELLANEOUS Transformer V X 4 MHZ LCD 6X Liquid Crystal Display Sw Double Pole Double Way Switch PR LCD C0 J4 J5 lcd79 equ h'9' tm_cnt equ h'a' time_f equ h'b' ttl_in equ h'c' w_save equ h'd' s_save equ h'e' cnt500u equ h'f' cntm equ h'0' ra0 equ 0 ra equ ra equ ra equ ra4 equ 4 rb6 equ 6 org 0 goto init org 4 goto int org 5 init movlw b' ' movwf trisa movlw b'00000' movwf option_reg J6 J7 J8 C9 X C8

4 movlw h'ff' movwf trisb bcf porta,ra bcf porta,ra movlw h'fe' movf portb,w xorlw h'ff' andlw h'0f' movwf c0m movlw h'ff' movf portb,w xorlw h'ff' andlw h'0f' movwf c0m call led_cont goto sw_check movf c0m,w btfsc status,z goto stand_by sw_check: bsf trisb,rb6 Fig. : PCB Layout of Microcontroller Based Inductance Capacitance Meter. movlw b' ' bsf porta,ra movwf porta bcf porta,ra movlw lcd7_0 movwf lcd70 movlw lcd7_ btfsc portb,rb6 movwf lcd7 goto stand_by movlw lcd7_ movwf lcd7 Start: movlw lcd7_ bcf porta,ra movwf lcd7 movlw lcd7_4 movlw d'55' movwf lcd74 movlw lcd7_5 movlw d'4' movwf lcd75 movlw lcd7_6 movwf tmr0 movwf lcd76 movlw lcd7_7 movlw d'' movwf lcd77 movlw lcd7_8 movlw d'46' movwf lcd78 movlw lcd7_9 movwf tm_cnt movwf lcd79 movlw h'a0' clrf c0s movwf intcon clrf c0s loop: bsf time_f,0 call led_cont stand_by:

5 movf time_f,w btfsc status,z goto time_out btfsc porta,ra4 goto loop time_out clrf intcon goto init clrf trisb bcf porta,ra bsf porta,ra Movf c0m,w bsf porta,ra movf c0s,w ttl_7lcd movlw lcd70 addwf ttl_in,w movwf fsr movf indf,w movwf portb tm movlw movwf cntm tmlp movlw d'49' movwf cnt500u tmlp nop nop decfsz cnt500u,f goto tmlp decfsz cntm,f goto tmlp int: goto tmlp decfsz cntm,f goto tmlp int: movwf w_save movf status,w movwf s_save btfsc intcon,t0if goto timer_int movf s_save,w movwf status swapf w_save,f swapf w_save,w retfie timer_int: bcf intcon,t0if movlw d'55' movlw d'4' movwf tmr0 decfsz tm_cnt,f movlw d'' int_end movlw d'46' movwf tm_cnt decfsz c0s,w movf c0m,w time_out: clrf time_f movf c0s,w goto cd_c0s movlw 9 movwf c0s goto cd_c0s movlw 5 movwf c0s movf c0m,w goto cd_c0m movlw 9 movwf c0m goto cd_c0m goto time_out cd_c0s: decf c0s,f cd_c0s: decf c0s,f cd_c0m: decf c0m,f cd_c0m: decf c0m,f End

About LC Meter This is one of the most accurate and simplest LC inductance / capacitance Meters that one can find, yet one that you can easily build y

About LC Meter This is one of the most accurate and simplest LC inductance / capacitance Meters that one can find, yet one that you can easily build y Home Electronic Store Electronic Blog Electronic Schematics Tutorials Downloads Lin Very Accurate LC Meter based on PIC16F84A IC. LC Meter Part's List: 2x 1K 2x 6.8K 1x 47K 3x 100K 1x 10K POT 2x 10pF 1x