Pololu 38 kHz IR Proximity Sensor, Fixed Gain, Low Brightness

SKU: POLOLU-2461 Brand: Pololu

Retired Product

Replaced by: POLOLU-2579
This product has been replaced by: POLOLU-2579
This product is no longer available. This page is only for reference.

Overview

These sensor modules are based on Vishay’s TSSP77038 modulated infrared receivers. Unlike most IR receiver modules designed for remote control of appliances like televisions, the TSSP77038 has a fixed gain (sensitivity) that makes the sensor more predictable when used in proximity or reflectance sensors. The Pololu carrier module combines the TSSP77038 with an IR LED driven by a 555 timer-based circuit to make a complete sensor module that requires only a 3.3 V to 5 V power connection. An enable input allows control of whether or not the IR LED is on, and a digital output indicates whether or not an object is detected. The module is available in low-brightness and high-brightness versions, which provide detection ranges of up to approximately 12 inches (30 cm) and 24 inches (60 cm), respectively. The actual performance depends on many factors, including object size, reflectivity, and ambient lighting conditions.

we carry several through-hole IR receivers that work nicely with the high-brightness LED and 38 kHz modulation circuit of these proximity sensors: the TSSP58038 is a through-hole version of the surface-mount TSSP77038 detector on these proximity sensors, and the TSSP58P38 is a unique modulated IR receiver with an output that can be used to measure distance. You can use several of the proximity sensors with these discrete IR receivers to make sophisticated sensing solutions in which you enable one emitter at a time and monitor the reflections with the other sensors.

Using the sensor

Connections

The proximity sensor has four connections: ground (GND), logic power (VDD), digital detection indicator (OUT), and IR emitter enable (ENABLE).

The logic power, VDD, should be between 3.3 V and 5 V. Supplying less than 5 V will decrease the IR LED brightness and decrease the sensing range. To run the sensor at full brightness while powered at 3.3 V, bridge the surface mount jumper located on the emitter side of the board.

The OUT pin, which is high by default, remains low as long as the TSSP77038 receiver is detecting a sufficient signal. When at the edge of the detection range, this output will alternate between high and low. A red LED on the emitter side of the board is tied to this output and turns on when the pin goes low, providing a visual indication of when the sensor is detecting something.

The ENABLE pin turns off the IR emitter LED when it is set low. This pin is high by default and can be left disconnected if dynamic control of the IR emitter is not needed. A green LED on the emitter side of the board is connected in parallel with the IR LED, making it easy to tell when the IR LED is on.

The four connections are arranged with a 0.1″ spacing along the edge of the board for compatibility with solderless breadboards, connectors, and other prototyping arrangements that use a 0.1″ grid. You can solder wires directly to the board or solder in either the 4×1 straight male header strip or the 4×1 right-angle male header strip that is included.

Tuning the emitter frequency

The trimmer potentiometer on the receiver side of the sensor can be used to adjust frequency of the IR emitter LED. The sensing distance can be maximized by tuning for 38 kHz, or it can be intentionally detuned to shorten the sensing range. If you have the appropriate equipment, you can tune it by setting the actual frequency, but a simpler approach is to just observe the performance as you turn the pot. The sensor should work to at least some degree over the entire range of the pot.

Limitations

  • This sensor will only tell you if an object is within its sensing range, not how far away it is. At the edge of its detection range, the output will alternate between high and low as it sporadically detects (see the left oscilloscope capture below).
  • The sensor is merely looking at whether or not it is getting any signal back, so object size and reflectivity (to IR) will affect sensing range.
  • The sensing angle is relatively wide in both directions. The high-brightness version in particular might require extra consideration when mounting to prevent seeing surfaces parallel to the sensor’s line of sight. For many applications, additional shielding can be used to block undesirable sensing paths, such as reflections off of the ground, or to reduce interference from ambient lighting. When applying shielding, keep in mind that reflection off the shielding itself can cause undesired activation of the sensor.
  • This sensor can be triggered by ambient IR (e.g. from fluorescent lights; see the right oscilloscope capture below). Some optical shielding, such as by having the sensor mounted receiver-side-down when fluorescent lights are above, might mitigate this. Some advanced analysis of the correlation between the output and toggling of the enable input might also be used to mitigate ambient interference.
  • Multiple sensors can interfere with each other. Multi-module applications might require use of the enable inputs to limit interference.
Oscilloscope capture of typical Pololu 38 kHz IR proximity sensor output close to its threshold of detection.
Oscilloscope capture of typical Pololu 38 kHz IR proximity sensor output when it is weakly, moderately, and strongly affected by fluorescent lights (top to bottom).

Schematic diagram

This schematic is also available as a downloadable pdf (169k pdf).

This product is listed in:

Retired

Product Comments

Exact shipping can be calculated on the view cart page (no login required).

Products that weigh more than 0.5 KG may cost more than what's shown (for example, test equipment, machines, >500mL liquids, etc).

We deliver Australia-wide with these options (depends on the final destination - you can get a quote on the view cart page):

  • $3+ for Stamped Mail (typically 10+ business days, not tracked, only available on selected small items)
  • $6+ for Standard Post (typically 6+ business days, tracked)
  • $10+ for Express Post (typically 2+ business days, tracked)
  • Pickup - Free! Only available to customers who live in the Newcastle region (must order online and only pickup after we email to notify you the order is ready). Orders placed after 2PM may not be ready until the following business day.

Non-metro addresses in WA, NT, SA & TAS can take 2+ days in addition to the above information.

Some batteries (such as LiPo) can't be shipped by Air. During checkout, Express Post and International Methods will not be an option if you have that type of battery in your shopping cart.

International Orders - the following rates are for New Zealand and will vary for other countries:

  • $11+ for Pack and Track (3+ days, tracked)
  • $16+ for Express International (2-5 days, tracked)

If you order lots of gear, the postage amount will increase based on the weight of your order.

Our physical address (here's a PDF which includes other key business details):

Unit 18, 132 Garden Grove Parade
Adamstown
NSW, 2289
Australia

Take a look at our customer service page if you have other questions such as "do we do purchase orders" (yes!) or "are prices GST inclusive" (yes they are!). We're here to help - get in touch with us to talk shop.

Have a product question? We're here to help!

Write Your Own Review

Guides

The Maker Revolution

The Maker Revolution celebrates the creation of new devices and the modification of existing ones - ...
The Maker Revolution celebrates the creation of new devices and the modification of existing ones - ...

Projects

Raspberry Pi Video Looper Display Installation | Overshare Video Festival

IntroductionA suspended ceiling display of forty repurposed screens and displays, each screening cr...
IntroductionA suspended ceiling display of forty repurposed screens and displays, each screening cr...

Mailbox Delivery Notification System

Introduction During the Covid lockdown, I needed something to do. The Postman or woman does not de...
Introduction During the Covid lockdown, I needed something to do. The Postman or woman does not de...

PiicoDev Schematic System

Introduction: Hi everybody. Over the past few weeks, I have been working on an intuitive system th...
Introduction: Hi everybody. Over the past few weeks, I have been working on an intuitive system th...
Feedback

Please continue if you would like to leave feedback for any of these topics:

  • Website features/issues
  • Content errors/improvements
  • Missing products/categories
  • Product assignments to categories
  • Search results relevance

For all other inquiries (orders status, stock levels, etc), please contact our support team for quick assistance.

Note: click continue and a draft email will be opened to edit. If you don't have an email client on your device, then send a message via the chat icon on the bottom left of our website.

Makers love reviews as much as you do, please follow this link to review the products you have purchased.