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Code Issues Wiki Activity

Add virtual current sensor documentation

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..and remove a couple of defines I didn't use.
This commit is contained in:
tracernz 2015-01-16 22:47:10 +13:00
parent a37c6ee9ee
commit a81fad9cc2
2 changed files with 31 additions and 3 deletions
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32
docs/Battery.md
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@ -74,8 +74,19 @@ Enable current monitoring using the CLI command
feature CURRENT_METER feature CURRENT_METER
``` ```
Configure the current meter type using the `current_meter_type` settings as per the following table.
| Value | Sensor Type |
| ----- | ---------------------- |
| 0 | None |
| 1 | ADC/hardware sensor |
| 2 | Virtual sensor |
Configure capacity using the `battery_capacity` setting, which takes a value in mAh. Configure capacity using the `battery_capacity` setting, which takes a value in mAh.
If you're using an OSD that expects the multiwii current meter output value, then set `multiwii_current_meter_output` to `1` (this multiplies amperage sent to MSP by 10).
### ADC Sensor
The current meter may need to be configured so that the value read at the ADC input matches actual current draw. Just like you need a voltmeter to correctly calibrate your voltage reading you also need an ammeter to calibrate your current sensor. The current meter may need to be configured so that the value read at the ADC input matches actual current draw. Just like you need a voltmeter to correctly calibrate your voltage reading you also need an ammeter to calibrate your current sensor.
Use the following settings to adjust calibration. Use the following settings to adjust calibration.
@ -83,4 +94,23 @@ Use the following settings to adjust calibration.
`current_meter_scale` `current_meter_scale`
`current_meter_offset` `current_meter_offset`
If you're using an OSD that expects the multiwii current meter output value, then set `multiwii_current_meter_output` to `1`. ### Virtual Sensor
The virtual sensor uses the throttle position to calculate as estimated current value. This is useful when a real sensor is not available. The following settings adjust the calibration.
| Setting | Description |
| ----------------------------- | -------------------------------------------------------- |
| `current_meter_scale` | The throttle scaling factor [centiamps, i.e. 1/100th A] |
| `current_meter_offset` | The current at zero throttle [centiamps, i.e. 1/100th A] |
If you know your current at zero throttle (Imin) and maximum throttle(Imax) you can calculate the scaling factors using the following formulas where Tmax is maximum throttle offset (i.e. for `max_throttle` = 1850, Tmax = 1850 - 1000 = 850):
```
current_meter_scale = (Imax - Imin) * 100000 / (Tmax + (Tmax * Tmax / 50))
current_meter_offset = Imin * 100
```
e.g. For a maximum current of 34.2 A and minimum current of 2.8 A with `max_throttle` = 1850
```
current_meter_scale = (Imax - Imin) * 100000 / (Tmax + (Tmax * Tmax / 50))
= (34.2 - 2.8) * 100000 / (850 + (850 * 850 / 50))
= 205
current_meter_offset = Imin * 100 = 280
```

2
src/main/sensors/battery.h
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@ -20,8 +20,6 @@
#define VBAT_SCALE_DEFAULT 110 #define VBAT_SCALE_DEFAULT 110
#define VBAT_SCALE_MIN 0 #define VBAT_SCALE_MIN 0
#define VBAT_SCALE_MAX 255 #define VBAT_SCALE_MAX 255
#define VIRTUAL_CURRENT_MIN 0
#define VIRTUAL_CURRENT_MAX 0xffff
typedef enum { typedef enum {
CURRENT_SENSOR_NONE = 0, CURRENT_SENSOR_NONE = 0,