Nuts and Volts - September 2011

supply with enough head space to let the op-amp be comfortable and stay linear. Since no negative voltages are used, the negative supply only needs to be low enough to give clearance and can be any voltage lower than about -1.5V. You may want to use a second op-amp from a dual package as an output buffer (voltage follower), depending on the intended load. You can change V or R or both to change the range. Changing VRef changes both the span and the range. Use the offset adjust (R3) to make the output 10V when X is zero. Since there are tens of thousands of op-amps to choose from, it is probably best to look to your favorite store, see what they have, and consult the spec sheets. For increased accuracy, you could choose an instrumentation op-amp. The bandwidth is probably irrelevant depending on just what the resistance source is and how fast it changes.

Figure 1

Jim Brannan Santa Clara, CA

AMATEUR RADIO AND TV McGills Warehouse .................................. 50 Ramsey Electronics, Inc. ................... 20-21 V-Module ................................................. 42

BATTERIES/CHARGERS Cunard Associates .................................. 27

BUYING ELECTRONIC SURPLUS Jaycar Electronics .................................... 57 Weirdstuff Warehouse ............................. 27

CCD CAMERAS/VIDEO Circuit Specialists, Inc. ....................... 82-83 Ramsey Electronics, Inc. ................... 20-21

CIRCUIT BOARDS AP Circuits .............................................. 33 Cunard Associates .................................. 27 Digilent .................................................... 19 Dimension Engineering .............................. 9 ExpressPCB ............................................ 55 Front Panel Express LLC ........................79 PCB Pool ................................................. 75 Saelig Company Inc. ............................... 33 V-Module ................................................. 42

COMPONENTS Cana Kit Corp. ........................................ 63 Electronix Express .................................. 13 Fun Gizmos ............................................. 27 Noritake ................................................... 32 V-Module ................................................. 42

COMPUTER
Hardware
Noritake ................................................... 32
Weirdstuff Warehouse ............................. 27
Microcontrollers / I/O Boards
Abacom Technologies ............................. 42
Bitscope .................................................... 4
Chipino .................................................... 27
Fun Gizmos ............................................. 27
I2I Controls................................................ 51
microEngineering Labs .............................. 5
MikroElektronika ........................................ 3
Parallax, Inc. .............................Back Cover
Pololu Robotics & Electronics .................. 43
Solarbotics/HVW ....................................... 9

DESIGN/ENGINEERING/ REPAIR SERVICES Cana Kit Corp. ........................................ 63 ExpressPCB ............................................ 55 Front Panel Express LLC ........................79 PCB Pool ................................................. 75

EDUCATION BaneBots ................................................... 8 Bitscope .................................................... 4 Blue Wolf .................................................. 25 Command Productions ............................ 25 Digilent .................................................... 19 Global Specialties ..................................... 7 GSS Tech Ed ........................................... 50 McGills Warehouse .................................. 50 NKC Electronics ...................................... 27 PAiA ......................................................... 33 Poscope ................................................... 18

EMBEDDED TOOLS I2I Controls................................................ 51 NetBurner .................................................. 2

ENCLOSURES Front Panel Express LLC ........................79 Integrated Ideas & Tech. ......................... 41

KITS & PLANS Cana Kit Corp. ........................................ 63 GSS Tech Ed ........................................... 50 Jaycar Electronics .................................... 57 NetBurner .................................................. 2 NKC Electronics ...................................... 27 PAiA ......................................................... 33 QKITS....................................................... 27 Ramsey Electronics, Inc. ................... 20-21 Solarbotics/HVW ....................................... 9

MISC./SURPLUS All Electronics Corp. ................................ 81 Front Panel Express LLC ........................79 Weirdstuff Warehouse ............................. 27

MOTORS BaneBots ................................................... 8

OPTICS
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SATELLITE Lemos International Co., Inc. .................. 27

TEST EQUIPMENT Bitscope .................................................... 4 Circuit Specialists, Inc. ....................... 82-83 Dimension Engineering .............................. 9 Global Specialties ..................................... 7 Jaycar Electronics .................................... 57 McGills Warehouse .................................. 50 NKC Electronics ...................................... 27 Poscope ................................................... 18 Saelig Company Inc. ............................... 33

TOOLS MikroElektronika ........................................ 3 NetBurner .................................................. 2 PanaVise ................................................. 13 Poscope ................................................... 18

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Abacom Technologies ........................... 42 All Electronics Corp. ............................. 81 AP Circuits ............................................ 33 BaneBots ................................................ 8 Bitscope .................................................. 4 Blue Wolf................................................ 25 Cana Kit Corp. ...................................... 63 Chipino .................................................. 27 Circuit Specialists, Inc. .................... 82-83 Command Productions ......................... 25 Cunard Associates ................................ 27 Digilent .................................................. 19 Dimension Engineering............................ 9 Electronix Express ................................ 13 ExpressPCB .......................................... 55 Front Panel Express LLC .....................79 Fun Gizmos .......................................... 27 Global Specialties ................................... 7 GSS Tech Ed ........................................ 50 I2I Controls.............................................. 51 Integrated Ideas & Tech. ....................... 41 Jaycar Electronics.................................. 57 Lemos International Co., Inc. ................ 27 Lynxmotion, Inc. .................................... 49 McGills Warehouse................................ 50 microEngineering Labs ............................ 5 MikroElektronika ..................................... 3 NetBurner ................................................ 2 NKC Electronics .................................... 27 Noritake ................................................. 32 PAiA ...................................................... 33 PanaVise ............................................... 13 Parallax, Inc. ..........................Back Cover PCB Pool .............................................. 75 Pololu Robotics & Electronics................ 43 Poscope ................................................. 18 QKI TS .................................................... 27 Ramsey Electronics, Inc. ................. 20-21 Robot Power ......................................... 27 Saelig Company Inc. ............................. 33 Solarbotics/HVW ..................................... 9 Twin Peaks Robotics ............................. 27 V-Module ............................................... 42 Weirdstuff Warehouse ........................... 27