Difference between revisions of "Analog Whacker"
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| + | == Analog Whacker -- An Analog Input Signal Conditioner for the UBW USB BitWhacker == | ||
| − | *Name: | + | *Name: Analog Wacker ( Whacker ) |
*Status: Concept, developing. | *Status: Concept, developing. | ||
*Technology: Operational Amplifiers | *Technology: Operational Amplifiers | ||
*Author: [[russ_hensel]] ( where you can find an email address to reach me ) | *Author: [[russ_hensel]] ( where you can find an email address to reach me ) | ||
| + | |||
| + | |||
| + | The purpose of this project is to provide a board which will condition analog signals so that the UBW can convert the analog signals to digital ones. We will also be providing specialized software to make working with the hardware more useful. | ||
| + | |||
| + | == Issuses for Input to Analog Pins == | ||
| + | |||
| + | Input to analog pins involves several issues. A few of the most basic and our approach to dealing with them will be discussed here. | ||
| + | |||
| + | * The voltage you have may not be the voltage you want. The UBW typically wants a voltage from 0 to 5 volts. We will use a gain controlled operational amplifier to either amplify or attenuate the input voltage. Thus a analog therometer with an output of 0 to 1 volt will be amplified to 0 to 5 volts. | ||
| + | |||
| + | *These inputs are not entirely passive. Often they present a high impedance, but during the sampling period they have a substantial capacitance. This if they are driven from a high impedance you will not get an accurate sample of the input. A common solution to this is to drive them from an operational amplifier. This is what this circuit does. | ||
| + | |||
| + | *A second problem is that the inputs measure only positive voltages. An op amp again offers a solution to this, either by inverting the input or by offsetting the voltage from zero. We are using non inverting amplifier, but providing for offset. | ||
| + | |||
| + | *Input pins should not be driven above the voltage of the PIC power supply or below zero. We will use diodes to limit these voltages. | ||
| + | |||
| + | == Guidelines for the Project == | ||
| + | |||
| + | *Circuit board should be single sided and be fairly easily etched using toner transfer. | ||
| + | *Board should support different configurations depending on how it is populated and how jumpers are placed. | ||
| + | *Common parts should be used. | ||
| + | |||
| + | |||
| + | == Ideas == | ||
| + | |||
| + | Single ended input, for ballanced input or current monitor, will need a seperate board. | ||
| + | |||
| + | single ended supply – invert in software | ||
| + | do not accurately 0, do in software but use 1 percent to center on 0 ( maybe even power from a port so can center or not ) | ||
| + | |||
| + | Add calibrate to the BitWhacker app | ||
| + | |||
| + | Just diodes for over under voltage protect | ||
| + | |||
| + | Current monitor on separate board | ||
| + | |||
| + | Offset for say diode temp – limit number | ||
| + | |||
| + | gain of 50 max, use jump to shift or what. | ||
| + | |||
| + | |||
| + | connect to BitWhacker how | ||
| + | |||
| + | 5 volt reference from local 5v reg, | ||
Revision as of 07:15, 4 April 2008
Contents
Analog Whacker -- An Analog Input Signal Conditioner for the UBW USB BitWhacker
- Name: Analog Wacker ( Whacker )
- Status: Concept, developing.
- Technology: Operational Amplifiers
- Author: russ_hensel ( where you can find an email address to reach me )
The purpose of this project is to provide a board which will condition analog signals so that the UBW can convert the analog signals to digital ones. We will also be providing specialized software to make working with the hardware more useful.
Issuses for Input to Analog Pins
Input to analog pins involves several issues. A few of the most basic and our approach to dealing with them will be discussed here.
- The voltage you have may not be the voltage you want. The UBW typically wants a voltage from 0 to 5 volts. We will use a gain controlled operational amplifier to either amplify or attenuate the input voltage. Thus a analog therometer with an output of 0 to 1 volt will be amplified to 0 to 5 volts.
- These inputs are not entirely passive. Often they present a high impedance, but during the sampling period they have a substantial capacitance. This if they are driven from a high impedance you will not get an accurate sample of the input. A common solution to this is to drive them from an operational amplifier. This is what this circuit does.
- A second problem is that the inputs measure only positive voltages. An op amp again offers a solution to this, either by inverting the input or by offsetting the voltage from zero. We are using non inverting amplifier, but providing for offset.
- Input pins should not be driven above the voltage of the PIC power supply or below zero. We will use diodes to limit these voltages.
Guidelines for the Project
- Circuit board should be single sided and be fairly easily etched using toner transfer.
- Board should support different configurations depending on how it is populated and how jumpers are placed.
- Common parts should be used.
Ideas
Single ended input, for ballanced input or current monitor, will need a seperate board.
single ended supply – invert in software do not accurately 0, do in software but use 1 percent to center on 0 ( maybe even power from a port so can center or not )
Add calibrate to the BitWhacker app
Just diodes for over under voltage protect
Current monitor on separate board
Offset for say diode temp – limit number
gain of 50 max, use jump to shift or what.
connect to BitWhacker how
5 volt reference from local 5v reg,
