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more thermistor update

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Dave Blundell 2020-05-12 14:49:53 -04:00
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FAQ-Basic-Wiring-and-Connections.md
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@ -43,5 +43,5 @@ The two basic kinds of general-purpose inputs are categorized as "digital" and "
Digital inputs need to have a pull resistor in order to ensure they do not pick up interference and trigger falsely. Most (double check your hardware!) digital inputs are configured with a pull-up resistor. Switches "turn on" the input by connecting it to a ground signal. When the switch is open, the pull-up resistor ensures that the hardware can see the difference. Most hardware implementations have basic protection circuitry to allow inputs to see battery voltage without damage. (double check your hardware!) Most switches in an engine bay such as power steering pressure, AC pressure, brake pressure switch, many PRNDL switches on automatic transmission shifters, oil "idiot" pressure, diagnostic enable, etc. are wired so that the other end connects to ground. This makes digital inputs ideal for monitoring most on-off type switches. Digital inputs need to have a pull resistor in order to ensure they do not pick up interference and trigger falsely. Most (double check your hardware!) digital inputs are configured with a pull-up resistor. Switches "turn on" the input by connecting it to a ground signal. When the switch is open, the pull-up resistor ensures that the hardware can see the difference. Most hardware implementations have basic protection circuitry to allow inputs to see battery voltage without damage. (double check your hardware!) Most switches in an engine bay such as power steering pressure, AC pressure, brake pressure switch, many PRNDL switches on automatic transmission shifters, oil "idiot" pressure, diagnostic enable, etc. are wired so that the other end connects to ground. This makes digital inputs ideal for monitoring most on-off type switches.
As of May 2020, analog inputs are broken into two basic categories: As of May 2020, analog inputs are broken into two basic categories:
1. "Thermistor" inputs have an internal pull up to 5V (varies according to hardware: 2.7k on proteus) to make connecting to sensors like coolant temp and air temperature easier. When using a thermistor input, one terminal of the sensor is connected to the ECU and the "other" end of your sensor should be connected to sensor ground. 1. "Thermistor" inputs have an internal pull up to 5V (varies according to hardware: 2.7k on proteus) to make connecting to sensors like coolant temp and air temperature easier. When using a thermistor input, one terminal of the sensor is connected to the ECU and the "other" end of your sensor should be connected to sensor ground. Note: many "single wire" thermistors used for coolant temperature have metal threads which make contact with the cylinder head/block, providing the "other" terminal without a wire.
1. "Analog Voltage" inputs have a **weak** pull-down to sensor ground (varies according to hardware: 500k on proteus) and are intended for things like MAP or TPS sensors that drive a voltage. On most hardware implementations(double check your hardware!), these inputs are also protected against excessive voltage. The combination of an internal pull-down resistor and built-in protection means that analog inputs can safely double as "active high" inputs, where battery voltage indicates that a switch is high. 1. "Analog Voltage" inputs have a **weak** pull-down to sensor ground (varies according to hardware: 500k on proteus) and are intended for things like MAP or TPS sensors that drive a voltage. On most hardware implementations(double check your hardware!), these inputs are also protected against excessive voltage. The combination of an internal pull-down resistor and built-in protection means that analog inputs can safely double as "active high" inputs, where battery voltage indicates that a switch is high.