Cable Tracer MT2202

1

This project used PIC24FJ64A004 and Bonus Part MCP6S26. The Cable Tracer is a device to detect underground cables. It was designed and tested on un-energized electric power cables but could be used on any underground cable. A 125 Khz signal is injected into the underground cable. A pickup coil receives a sample of this field. The strength of this field will indicate the presence and direction of the cable. The Receiver consists of a PreAmp and Detector made from an RFID Chip (MCP2030). The RSSI signal strength output is amplified by a Variable Gain Amplifier (MCP6S26). The amplified output feeds an Analog Meter to provide a visual indication of the signal strength. The meter also has a sensitivity control which allows the meter to have enough sensitivity to indicate the direction of the cable by slightly rotating the pickup coil. The RSSI signal is fed to an A/D input on the PIC24FJ64GA004. It also feeds a Comparator input. The A/D channel is used to drive an audio Variable Frequency Oscillator based on a Timer Output to provide an audio indication of the signal strength similar to a Metal Locator. The Comparator is used to indicate a course signal strength that is used in conjunction with the A/D value to determine if the VGA should change the strength of the signal. A 7 Segment LCD display is used to indicate the amplification factor of the VGA. An LCD is used to conserve battery power. The AC drive to the display is provided by an output port in conjunction with the firmware. This indication is used to determine if the signal source is at an appropriate level. With some operator practice it will also help indicate relative depth changes and/or cable breaks. There is also a Auto/Manual switch, Up, and Down buttons. In some cases Manual Operation of the amplification factor is useful. Another comparator is used to monitor Battery voltage. An LED is used to indicate a Low Battery condition. The battery is four AA batteries to provide 6 volts. The 6 volt battery supplies the power to a 3.3V Low Drop Out regulator (MCP1700). The power consumption of the Cable Tracer is low enough to not cause heating of the LDO. The 6 volt source and LDO provide a reasonable amount of operational time before the battery discharges to an unusable level. The Peripheral Pin Select was particularly useful in selecting the desired features of the microcontroller for this application.

MCP2030

RCVR VGAMCP6S26

3.3V REGMCP1700

24FJ64GA004

METER

Cable Tracer MT2202

2

Title

Size Document Number Rev

Date: Sheet of

MT2202 0

ANALOG

A

1 3Wednesday , October 10, 2007

GN

D1

CS 2

SCLK/ALERT 3

RSSI 4

LFDATA/CCLK/SDIO 6

VDD

17

VDD

28

LCZ9

LCY10

LCX11

LCCOM13

U1

MCP2030L12MHY

C562PF

C2.1UF

C1.1UF

+3.3V

R1100K

SDIRCVR

SCKRCVR

RCVRCS#

RSSI

PGACS#

PGADI

PGACLK

C4.1UF

+ C310UF

D11N4001

D21N4001

C13.1UF

I

M1

500 uA

R3 150

OUT 1CH02

Vref 8

GN

D9

CS10SI11SCK13

VCC

14

CH13

CH24

CH35

CH46

CH57

SO 12

U2

MCP6S26

R210K

Cable Tracer MT2202

3

Title

Size Document Number Rev

Date: Sheet of

MT2202 0

PROCESSOR

A

2 3Thursday , October 04, 2007

C810UF

SEGB

C7.1UF

C6.1UF

123456

J1

CON6

+3.3V

SEGC

R4

47K

SDIRCVR

CSRCVR#

SCKRCVR

SEGDRSSI

PGADI

PGACS#

PGACLK

VBAT

AOUT

R7 27K

R5330

D3LED

SEGE

R610K

R910K

SEGFSEGG

UPAUTO/MAN

R815K

AUTO/MANLED

RP9/SDA1/CN21/PMD3/RB9 1

RP22/CN18/PMA1/RC6 2RP23/CN17/PMA0/RC7 3RP24/CN20/PMA5/RC8 4RP25/CN19/PMA6/RC9 5

DISVREG6

Vcap/Vddcore 7

PGD2/EMUD2/RP10/CN16/PMD2/RB10 8PGC2/EMUC2/RP11/CN15/PMD1/RB11 9AN11/RP13/CN13/PMRD/RB13 11

AN12/RP12/CN14/PMD0/RB12 10

RA10/PMA10/TMS12

RA7/PMA7/TCK13

AN10/CVref /RTCC/RP14/CN12/PMWR/RB14 14AN9/RP15/CN11/PMCS1/RB15 15

AGN

D16

AVD

D17

MCLR18

RA0/CN2/Vref +/AN019 RA1/CN3/Vref -/AN120

PGD1/EMUD1/AN2/C2IN-/RP0/CN4/RB0 21PGC1/EMUC1/AN3/C2IN+/RP1/CN5/RB1 22AN4/C1IN-/RP2/SDA2/CN6/RB2 23AN5/C1IN+/RP3/SCL2/CN7/RB3 24

AN6/RP16/CN8/RC0 25AN7/RP17/CN9/RC1 26AN8/RP18/CN10/PMA2/RC2 27

VDD

128

GN

D1

29

RA2/CN30/CLKI/OSCI30

RA3/CN29/CLKO/OSCO31

RA8/PMA8/TDO32

SOSCI/RP4/CN1/RB4 33

RA4/CN0/T1CK/SOSCO34

RA9/PMA9/TDI35

RP19/CN28/PMBE/RC3 36RP20/CN25/PMA4/RC4 37RP21/CN26/PMA3/RC5 38

GN

D2

39VD

D2

40

PGD3/EMUD3/RP5/SDA1/CN27/PMD7/RB5 41PGC3/EMUC3/RP6/SCL1/CN24/PMD6/RB6 42RP7/INT0/CN23/PMD5/RB7 43RP8/SCL1/CN22/PMD4/RB8 44

U3

PIC24FJXXGA004

SEGDPSEGCOM

DWN

LOW BAT

SEGA

Title

Size Document Number Rev

Date: Sheet of

MT2202 0

MISC

A

3 3Thursday , October 04, 2007

SW2

SW3

SW4

R12100

D4LED

Q12N3904

Q22N3906

R10100

+ C9100UF

+

C10

100UF LS1

SPEAKER

AOUT

+3.3V

AUTO/MANLED

+3.3V

BT16V

CO

M1

A115

B114

C1

5

D1

4

E13

F116

DP2

6

A211

B210

C2

9

D2

8

E27

F212

G2

13

G1

17

DP1

2

A A

B B

C C

D D

E E

F F

G G

. .DP1 DP2

U4

2DIGITLCD

SEGA

SEGC

SEGGSEGFSEGESEGD

SEGB

GN

D1

OUT 2IN3U5

MCP1700C111UF

C121UF

R134.7K

R144.7K

R154.7K

SW1POWER

SEGCOM

SEGDP

+3.3V

VBAT

UP

DWN

AUTO/MAN

R11100

Cable Tracer MT2202

4

while(1) { ADConvert(); //Get RSSI Value loopct++; for (x=0; x < 0x7FFF;x++); //Delay if(AUTOMANSW == 0) //Push Button Pressed { while(AUTOMANSW == 0); //wait for release AUTOLED = ~AUTOLED; //Toggle Mode } if(AUTOLED == 1) //If MANUAL Mode { if(UPSW == 0) { while(UPSW == 0); if(gain < 0x4007) { gain++; //Boost Gain PGACS = 0; //Select PGA SPI1BUF = gain; while(SPITBF == 1); //Wait for empty for (x=0; x<= 10;x++); //Delay PGACS = 1; LCDout(gain & 0x0007); //Out gain setting }//end gain < 4007 }//end UPSW if(DWNSW == 0) { while (DWNSW == 0); if(gain > 0x4000) { gain--; //Drop Gain PGACS = 0; //Select PGA SPI1BUF = gain; while(SPITBF == 1); //Wait for empty for (x=0; x<= 10;x++); //Delay PGACS = 1; c2flag = 0; LCDout(gain & 0x0007); }//end gain > 4000 }//end DWNSW }//end AUTOLED == 1 else _C2EN = 1; //Enable for AUTO Mode if(loopct >= LOOP) { if((c2flag == 1)&(AUTOLED == 0)) //Gain too high { if(gain > 0x4000) { gain--; //Drop Gain

Cable Tracer MT2202

5

PGACS = 0; //Select PGA SPI1BUF = gain; while(SPITBF == 1); //Wait for empty for (x=0; x<= 10;x++); //Delay PGACS = 1; c2flag = 0; LCDout(gain & 0x0007); _C2EN = 1; //Re Enable after GAIN drop }//end gain>0x4000 }//end c2flag == 1 if((ADValue < GAIN_TRIP)&(AUTOLED == 0)) //Gain too low { if(gain < 0x4007) { gain++; //Boost Gain PGACS = 0; //Select PGA SPI1BUF = gain; while(SPITBF == 1); //Wait for empty for (x=0; x<= 10;x++); //Delay PGACS = 1; LCDout(gain & 0x0007); //Out gain setting }//end gain < 4007 }//end ADValue < GAIN_TRIP loopct = 0; }//end loopct >= LOOP ADValue = ADValue & 0x03FF; //10 bits //Oscillator PR4 = 1 = 32Khz

// PR4 = 03FF = 60 Hz //Divide value by 2 for 120 to 15Khz ADValue = 0x03FF - ADValue; //Get as low to high on pitch if(ADValue > 2) ADValue = ADValue / 2; else ADValue = 1; TMR4 = 0x0000; //Clear Reg, Otherwise might miss compare PR4 = ADValue; //Load Oscillator //0x3FF 16 mS 60Hz //0x001 31.2Khz 32 uS

Cable Tracer MT2202

6