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TuxMicro Devices

 

 ULTRASONIC PROXIMITY AND DISTANCE SENSOR MODULE

URFDASM

  URF 1000 DSM 

Prototype sample PCB


 Ultrasonic Proximity and Distance Sensor Module

 The URF 1000 series ultrasonic sensing modules provide distance measurement capability to embedded microcontroller or SBC devices. The URF 1000 control module (DSM) implements both proximity and distance measurement in a single embedded device. The URF 1000 series detection devices can detect stationary objects up to 3 meters. Distance measurement is implemented via a host controller which triggers and receives a modulated TTL signal which can beused by a microcontroller to calculate distance via 40KHz ultrasonic bursts.


In proximity detection mode the DSM can detect the presence of stationary and non stationary objects by providing the host with single TTL logic pulse.This logic can then be used by a host to signal other I/O devices upon detection. It is simple to use the DSM with BASIC Stamp®, Javelin Stamp, Atmel AVR,Arduino and PIC microcontrollers. The DSM works by emitting a series of controlled ultrasonic bursts and then timing the bursts until an echo response isdetected. Once the echo response time is calculated a time envelope is provided as an output pulse (PWM) that encapsulates the time elapsed from burst to echo sense. Simply by measuring the time of the echo from burst interval the distance to target can easily be pulse width modulated and sent to a host controller.


Features

  • Supply Voltage – 5.5 to 12 VDC H1 (pins 1 Vdd & 2 Vss)
  • Supply Current – 25 mA typ
  • Echo Range – 10 mm to 2 m typ (3 m max)
  • Trigger (SIG/IN H1 pin 4) – Active Low TTL pulse, tIn 25Cs typ. (5us min)
  • Echo Time (T1/OUT H1 pin 3) – Active High TTL pulse, tEcho 25µs to 32 ms
  • Echo delay – 350µs from Trigger, ADC/AN1 signal detect > 3.125Vdc
  • Burst Frequency – 40 kHz
  • Burst Time Period – 300µs
  • Time between measurements – 13ms
  • Two pin I/O control port (SIG/IN and T1/OUT) via H1
  • 4MHz Crystal controlled time reference
  • Burst amplitude control
  • Echo gain control





Module Dimensions

   75 mm L x 50 mm W x 15mm H (2.95in x 1.96 in x 0.59 in)


Technical Description

The DSM module detects objects by emitting a series of ultrasonic bursts and then timing the echo response. A control trigger (active low TTL pulse - trailing edge) of a host microcontroller port enables the DSM to emit short 40 kHz ultrasonic bursts. A single burst at 40KHz propagates at around 344 m/sec (.344 mm/µs or 0.013543"/µs) strikes an object and is echoed to the receive 400SR16 ultrasonic transducer. The DSM then provides a PWM output to the host via H1-3 which encapsulates the time delay in microseconds (µs) measured between burst to echo.


Trigger SIG/IN

Trigger SIG/IN (H1 pin 4) – Active Low TTL pulse, 25us typical (5µs min) remains at a continuous logic high TTL state. A host microcontroller output triggers a new measurement upon initiating a trailing edge (trigger signal). An Echo delay is assumed during the initial Burst interval from which time the echo timer (TMR1) begins to increment at 1 µs intervals 1/(FOSC/4). The timer will continue to run until either the ADC/AN1 signal (H2-5) is detected (350 µs min) or the timer reaches its preset timeout (33ms typ). The default T1/OUT (TMR1) timer is preset to 8000H (maxecho) and will reset upon overflowing from FFFFH to 0000H. This allows for a max measurement time of 32.767ms since TMR1 FOSC/4 = 1 µs.


T1/OUT

The T1/OUT (H1 pin 3) pulse width in microseconds reflects the active high H1-3 (T1/OUT) measurement. Pulse width corresponds to x/1 tDistance to the target (.344 mm/µs or 0.013543"/µs). If an echo response is not received within a 33ms window the DSM will reset (for new measurement and will not generate a H1-3 (T1/OUT) measurement pulse. T1/OUT measurement pulse width range (tEcho) 25µs @ 5mm to 32 ms (max). The 5mm @ 25µs standard mark is used as a zero reference (calibration) to obtain accurate distance calculations.


H1 Port 4 Pin I/O CONTROL (TTL IO)  

H1-1

Vdd 6-12Vdc

H1-2

GND

H1-3

T1/OUT Echo Time active high TTL pulse, tEcho 25µs to 32 ms

H1-4

SIG/IN Trigger active low TTL pulse, 25µs  typ. (5µs  min)

 

 



 H2 Port 5 Pin ICSP  

H2-1

Vpp (programming voltage 13.2vdc max)

H2-2

Vdd 5-5.5vdc

H2-3

GND

H2-4

PGD ICSP (ICSPDAT) or T1/OUT

H2-5

PGC ICSP (ICSPCLK) or ADC/AN1 detect signal > 3.125 Vdc 

 



H1-4 .100 header (2.5mm) allows the module to be plugged into a solderless breadboard. Header H1 compatible with Microchip PICKit series programmer/debuggers. 

 


The DSM maintains H2 a 5-pin header used to provide PIC compatible ICSP signals. This .100 header allows the module to be plugged into a programmer/ debugger which supports PIC ICSP.  Resistor R16 is omitted during initial development and should not be installed until U1 device firmware has been downloaded to DSM controller. This prevents accidental erasure of controller via H2 port. URF 1000 DSM supports the Microchip ICSP specification DS30277D.          

 

 

TMR1 (T1/OUT) Distance Calculation

 

tDistance – elapsed time in seconds after sending burst (T1/OUT) pulse

tEcho – actual echo time in microseconds (µs)

 

FOSC = 4MHz

 

maxecho = 32768 (8000H)

 

tDistance = (TMR1H:TMR1L – maxecho) * 1/(FOSC/4)

 

tEcho = tDistance/2 * 1000000

 

Distance (mm) = tEcho * .344424

 

Maximum measurable distance to object 5642.87 mm (18.51’) @ maxecho

 

Distance Lab Test:

 

4x4” piece of cardboard suspended 100mm above DSM produced distance (T1/OUT) pulse width (tDistance) of 580us 30% duty cycle.  See controller interface specifications on Page 7.

 

Notes: 

 

Transducer 400ST16 @ 119dB max echo distance is around 10 feet with maximum driving voltage @ 20 Vrms. Directivity is 0 - 20° with maximum distance possible at 0°. Sensitivity @ f0 for 400SR16 is -65dB. Center Frequency (f0) set @ 40.0KHz±1.0KHz

 

Specifications

 

Host Interface Signals H1 Port

 

urf-1000-graph

 

 

 urf-transciever-specs.

 


 spl db





 

Distance Measurements

 

H2-5 DC gain = 1.60Vdc

DC power (pin-6) of U3 = 16Vdc

 

 

Inches (mm)

T1/OUT timeOn

T1/OUT timeOff

TMR1H:L

46 (1168.4)

6.8ms

5.8ms

0x8626h

43 (1092.2)

6.4ms

6.2ms

0x81D1h

40 (1016)

6.0ms

6.6ms

0x78CFh

37 (939.8)

5.6ms

7ms

0x6EBCh

34 (863.6)

5.2ms

7.4ms

0x6235h

30 (762)

4.5ms

7.9ms

0x5707h

24 (609.6)

3.5ms

8.9ms

0x4680h

18 (457.2)

2.8ms

9.6ms

0x3821h

12 (304.8)

1.8ms

10.6ms

0x21F3h

6 (152.4)

.81ms

11.6ms

0x1051h

3 (76.2)

.35ms

12.05ms

0x06A4h

1 (25.4)

95µs

13.3ms

0x01C4h

 

 

 

 

 

1 inch = 0.0254 meters (25.4mm)