| Manufacturer: | Parallax |
| Manufacturer's Part Number: | 28015N |
- Range - 2cm to 3m (~.75" to 10')
- Supply Voltage: 5V +/-10% (Absolute: Minimum 4.5V, Maximum 6V)
- Supply Current: 25 mA typ; 30 mA max
- 3-pin interface (power, ground, signal)
- 20 mA power consumption
- Narrow acceptance angle
- Simple pulse in / pulse out communication
- Indicator LED shows measurement in progress
- Input Trigger - positive TTL pulse, 2 uS min, 5 uS typ.
- Echo Pulse - positive TTL pulse, 115 uS to 18.5 mS
- Echo Hold-off - 350 uS from fall of Trigger pulse
- Burst Frequency - 40 kHz for 200 uS
- Size - 22 mm H x 46 mm W x 16 mm D (0.85 in x 1.8 in x 0.6 in)
So can this be use in place of the range finders at the DIY-Drones store.
Comments
@narwhal If you don't wait for a response, how do you know how long the return pulse was?
If your main loop runs at, say, 100 Hz, and you just check for the presence of the response pulse from the rangefinder, you will inevitably end up with a worst case error of 1/100th of a second.
That corresponds to 3.43 meters of error :)
I probably misunderstood the way you've implemented the rangefinding "thread", though.
I looked at this sonar briefly for arduCopter but did not pursue it because, as Ante says, this sonar has very little onboard processing so this extra work falls on the calling cpu (i.e the APm). It would need to force the ping to go out (no big deal) but then also keep checking the analog port to see if a return signal has been received. This would need to be done at a time when the processor isn't doing anything else important..you don't want your quad making a little jerk every time it checks the sonar.
for other purposes it might be a-ok of course.
How do u have it connected? Wiring diagram? what did u change in the code?
No. It doesn't have an analogue output and it requires additional processing (triggering the rangefinder, waiting for return, measuring the length of the pulse), which would tie up the uC on the APM for too long per loop cycle.
The only way you could use it would be to have a separate uC handling that job and outputting the result via one of its PWM pins, then put a suitable capacitor in parallel to that pin and the ground to get an analogue output.