Photo-gate timer - Revision history

Shawn: /* Program */ interrupts and precision

2025-04-26T00:44:17Z

Program: interrupts and precision

← Older revision		Revision as of 17:44, 25 April 2025
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	===Program===		===Program===
			Micro-controllers can be programmed in higher level languages like MicroPython and CircuitPython, a little "closer to the metal" with Arduino, or in the language built into the hardware. It is important to consider the difference in precision available according to the range of time the program takes to respond to the external signals from the photo-gates. It is best to use "hardware interrupts," available in only some programming environments.
	For examples, see [[Photo-gate timer with an Arduino]] or [[Photo-gate timer with CircuitPython]] or the less-accurate [[Photo-gate timer with a PICAXE 20M2]].		For examples, see [[Photo-gate timer with an Arduino]] or [[Photo-gate timer with CircuitPython]] or the less-accurate [[Photo-gate timer with a PICAXE 20M2]].
	#Initiate the display		#Initiate the display

Shawn: /* See also */

2025-04-23T17:04:43Z

Shawn: /* Specifications */ Power and speed options

2025-04-23T16:38:39Z

Specifications: Power and speed options

← Older revision		Revision as of 09:38, 23 April 2025
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	[[File:Photo-gate-timer-2014-03-11.jpg\|512px\|thumb\|right\|A photo-gate timer featuring an LCD display, showing 3 of 5 possible gates at left. In a working lab, the LEDs and photo-transistors would have to be attached to the board via long wires so they could be placed usefully.]]		[[File:Photo-gate-timer-2014-03-11.jpg\|512px\|thumb\|right\|A photo-gate timer featuring an LCD display, showing 3 of 5 possible gates at left. In a working lab, the LEDs and photo-transistors would have to be attached to the board via long wires so they could be placed usefully.]]
	===Specifications===		===Specifications===
	*Connect up to 5 gates ~~for four times (first gate zeros timer)~~.		*Connect up to 5 gates.
	*Include a display with enough characters to show the time past each connected gate~~, 8x2~~ or ~~16x2~~.		*Include a display with enough characters to show the time past each connected gate: Minimum 16x2 LCD.
	*Include a power switch to save the battery~~, and/or a~~ reset switch.		*Power by battery or USB.
			**Option: Power by rechargeable battery.
			**Option: Include a power switch to save the battery.
			*Expose reset switch.
	*Use a breadboard so it can be built by students, or modified.		*Use a breadboard so it can be built by students, or modified.
	*Allow timing of periods up to at least 10s, accurate to 0.01s.		*Allow timing of periods up to at least 10s, accurate to 0.01s or better.
			**Option: Time entry and exit at each gate to get local speed.

	===Circuit===		===Circuit===

Shawn: /* Datasheets */

2025-04-20T18:43:22Z

Datasheets

← Older revision		Revision as of 11:43, 20 April 2025
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	===Datasheets===		===Datasheets===
	[[File:1.5mm pitch pins soldered onto 2.5mm header.jpg\|300px\|thumbnail\|right\|Showing the 8 pins of the Newhaven LCD spread to fit onto a 0.1" pitch header, so as to be easily inserted into a solderless breadboard.]]		[[File:1.5mm pitch pins soldered onto 2.5mm header.jpg\|300px\|thumbnail\|right\|Showing the 8 pins of the Newhaven LCD, 1.5mm pitch, spread to fit onto a 0.1" (2.54mm) pitch header, so as to be easily inserted into a solderless breadboard.]]
	;Newhaven Display liquid crystal display module, with side white backlight and transflective display.:http://www.newhavendisplay.com/specs/NHD-C0216CiZ-FSW-FBW-3V3.pdf		;Newhaven Display liquid crystal display module, with side white backlight and transflective display.:http://www.newhavendisplay.com/specs/NHD-C0216CiZ-FSW-FBW-3V3.pdf
	;Atmel 328P 8-bit microcontroller: https://www.microchip.com/en-us/product/atmega328p		;Atmel 328P 8-bit microcontroller: https://www.microchip.com/en-us/product/atmega328p

Shawn: /* Components */ Expanding possibilities

2025-04-20T18:38:59Z

Components: Expanding possibilities

← Older revision		Revision as of 11:38, 20 April 2025
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	***NPN emitter resistor (~1kΩ) (~$0.02)		***NPN emitter resistor (~1kΩ) (~$0.02)
	*Breadboard (~$5)		*Breadboard (~$5)
	*Micro-controller. I ~~use~~ a PICAXE 20M2 (software timing) or a 20X2 (dedicated hardware timing for better accuracy); both have plenty of inputs and outputs for multiple gates and any type of display. ($4-$6)		*Micro-controller. There are many to choose from:
			**I first used a PICAXE 20M2 (software timing) or a 20X2 (dedicated hardware timing for better accuracy); both have plenty of inputs and outputs for multiple gates and any type of display. ($4-$6)
			**Since the 2010s, I have used a breadboard Microchip/Atmel 328P. You can easily program this with the Arduino system.
			**In the 2020s, I use Adafruit Feather. These are breadboard-friendly devices that include a battery-charger and many options for micro-controllers, like RP2040, ESP32, and Atmel 32u4. Some even have built-in displays.
	**Resonator circuit if necessary. Not available for PICAXE 20M2. (~$1)		**Resonator circuit if necessary. Not available for PICAXE 20M2. (~$1)
	*Display		*Display
	**LCD ~~Display~~, serial capable. I use Newhaven's NHD-C0216CiZ-FSW-FBW-3V3 LCD with I2C ($10)		**LCD display, serial capable. I use Newhaven's NHD-C0216CiZ-FSW-FBW-3V3 LCD with I2C ($10)
	***Two 1µF capacitors to aid voltage booster circuit.		***Two 1µF capacitors to aid voltage booster circuit.
	***Two 5kΩ resistors to pull up serial clock and data lines while idle.		***Two 5kΩ resistors to pull up serial clock and data lines while idle.
	***One 50kΩ resistor to pull up reset.		***One 50kΩ resistor to pull up reset.
	**~~Alternatively~~, a TTL-to-USB or TTL-to-serial circuit for sharing data with computer ($18)		**TFT display. These are bright displays, easier to read in dark situations, but use more power than LCDs.
			**7-segment display. You can use a 4-digit 7-segment display to display milliseconds or centiseconds
			*Could use a computer connection to enter data directly into a spreadsheet:
			**A TTL-to-USB or TTL-to-serial circuit for sharing data with computer ($18)
			**USB-HID-capable microcontroller boards like Adafruit's RP2040 Key Boar ($10), Arduino Leonardo, etc.
	*Hook-up wires ($2)		*Hook-up wires ($2)
	*Power supply		*Power supply
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	**3V AC adapter, or		**3V AC adapter, or
	**Two alkaline AAA or AA batteries.		**Two alkaline AAA or AA batteries.
			**5V adapter from 2000s era phones.
			**5V USB charger.

	====Saving power====		====Saving power====

Shawn: /* Datasheets */

2025-04-20T17:36:10Z

Datasheets

← Older revision		Revision as of 10:36, 20 April 2025
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	[[File:1.5mm pitch pins soldered onto 2.5mm header.jpg\|300px\|thumbnail\|right\|Showing the 8 pins of the Newhaven LCD spread to fit onto a 0.1" pitch header, so as to be easily inserted into a solderless breadboard.]]		[[File:1.5mm pitch pins soldered onto 2.5mm header.jpg\|300px\|thumbnail\|right\|Showing the 8 pins of the Newhaven LCD spread to fit onto a 0.1" pitch header, so as to be easily inserted into a solderless breadboard.]]
	;Newhaven Display liquid crystal display module, with side white backlight and transflective display.:http://www.newhavendisplay.com/specs/NHD-C0216CiZ-FSW-FBW-3V3.pdf		;Newhaven Display liquid crystal display module, with side white backlight and transflective display.:http://www.newhavendisplay.com/specs/NHD-C0216CiZ-FSW-FBW-3V3.pdf
	;Atmel 328P 8-bit microcontroller:~~http~~://www.~~atmel~~.com/~~devices~~/~~ATMEGA328P.aspx~~		;Atmel 328P 8-bit microcontroller: https://www.microchip.com/en-us/product/atmega328p
	;PICAXE micro-controller system for education:~~http~~://picaxe.com		;PICAXE micro-controller system for education: https://picaxe.com/software/
	;Lite-on LTE-302 side-look IR emitter: https://optoelectronics.liteon.com/upload/download/DS-50-92-0009/E302.pdf		;Lite-on LTE-302 side-look IR emitter: https://optoelectronics.liteon.com/upload/download/DS-50-92-0009/E302.pdf
	;Lite-on LTR-301 side-look IR photo-transistor: https://optoelectronics.liteon.com/upload/download/DS-50-93-0013/LTR-301.pdf		;Lite-on LTR-301 side-look IR photo-transistor: https://optoelectronics.liteon.com/upload/download/DS-50-93-0013/LTR-301.pdf

Shawn: /* Datasheets */ updated links to Lite-on semiconductors.

2025-04-20T17:35:13Z

Datasheets: updated links to Lite-on semiconductors.

← Older revision		Revision as of 10:35, 20 April 2025
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	;Atmel 328P 8-bit microcontroller:http://www.atmel.com/devices/ATMEGA328P.aspx		;Atmel 328P 8-bit microcontroller:http://www.atmel.com/devices/ATMEGA328P.aspx
	;PICAXE micro-controller system for education:http://picaxe.com		;PICAXE micro-controller system for education:http://picaxe.com
	;Lite-on LTE-302 side-look IR emitter:~~http~~://optoelectronics.liteon.com/upload/download/DS-50-92-0009/~~P_100_E302~~.pdf		;Lite-on LTE-302 side-look IR emitter: https://optoelectronics.liteon.com/upload/download/DS-50-92-0009/E302.pdf
	;Lite-on LTR-301 side-look IR photo-transistor:~~http~~://optoelectronics.liteon.com/upload/download/DS-50-93-0013/~~P_100_LTR~~-301.pdf		;Lite-on LTR-301 side-look IR photo-transistor: https://optoelectronics.liteon.com/upload/download/DS-50-93-0013/LTR-301.pdf

	===See also===		===See also===

Shawn: /* Program */

2025-03-30T21:12:16Z

Program

← Older revision		Revision as of 14:12, 30 March 2025
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	===Program===		===Program===
	For ~~an explicit example~~, see [[Photo-gate timer with an Arduino]] or the less-accurate [[Photo-gate timer with a PICAXE 20M2]].		For examples, see [[Photo-gate timer with an Arduino]] or [[Photo-gate timer with CircuitPython]] or the less-accurate [[Photo-gate timer with a PICAXE 20M2]].
	#Initiate the display		#Initiate the display
	#Write "waiting for 1st gate" to the display		#Write "waiting for 1st gate" to the display

Shawn: /* Components */

2025-03-29T20:46:02Z

Components

← Older revision		Revision as of 13:46, 29 March 2025
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	*Photogates		*Photogates
	**LED, infrared (~$0.15). I use a Lite-On LTE-302-M, which has a black or gold dot to identify itself as an emitter; it also allows up to 50mA of constant current, or even 1A if pulsed 300 10µs pulses per second, so it can be used at a greater distance than 20mA emitters. The cathode is the short lead, on the left as you're facing the lens.		**LED, infrared (~$0.15). I use a Lite-On LTE-302-M, which has a black or gold dot to identify itself as an emitter; it also allows up to 50mA of constant current, or even 1A if pulsed 300 10µs pulses per second, so it can be used at a greater distance than 20mA emitters. The cathode is the short lead, on the left as you're facing the lens.
	[[File:LTR-301-fov.png\|right\|The sensitivity of the 301 is very dependent on the angle of incidence of light. This helps mitigate interference, but one must be careful to aim the phototransistor.]]		[[File:LTR-301-fov.png\|256px\|thumb\|right\|The sensitivity of the 301 is very dependent on the angle of incidence of light. This helps mitigate interference, but one must be careful to aim the phototransistor.]]
	**Phototransistor, infrared (~$0.15). I use a Lite-On LTR-301, which has a red dot to identify itself as a receiver. The collector is the long lead, on the right as you're facing the lens, the short lead being the emitter of the transistor.		**Phototransistor, infrared (~$0.15). I use a Lite-On LTR-301, which has a red dot to identify itself as a receiver. The collector is the long lead, on the right as you're facing the lens, the short lead being the emitter of the transistor.
	**Switching transistor, 2N2222 or equivalent NPN (~$0.10). I use an R3309, whose leads are emitter, collector, and base, left to right, as seen leading down when looking at the flat face.		**Switching transistor, 2N2222 or equivalent NPN (~$0.10). I use an R3309, whose leads are emitter, collector, and base, left to right, as seen leading down when looking at the flat face.

Shawn: /* Components */ Diagram of angular dependence of sensitivity

2025-03-29T20:45:14Z

Components: Diagram of angular dependence of sensitivity

← Older revision		Revision as of 13:45, 29 March 2025
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	*Photogates		*Photogates
	**LED, infrared (~$0.15). I use a Lite-On LTE-302-M, which has a black or gold dot to identify itself as an emitter; it also allows up to 50mA of constant current, or even 1A if pulsed 300 10µs pulses per second, so it can be used at a greater distance than 20mA emitters. The cathode is the short lead, on the left as you're facing the lens.		**LED, infrared (~$0.15). I use a Lite-On LTE-302-M, which has a black or gold dot to identify itself as an emitter; it also allows up to 50mA of constant current, or even 1A if pulsed 300 10µs pulses per second, so it can be used at a greater distance than 20mA emitters. The cathode is the short lead, on the left as you're facing the lens.
			[[File:LTR-301-fov.png\|right\|The sensitivity of the 301 is very dependent on the angle of incidence of light. This helps mitigate interference, but one must be careful to aim the phototransistor.]]
	**Phototransistor, infrared (~$0.15). I use a Lite-On LTR-301, which has a red dot to identify itself as a receiver. The collector is the long lead, on the right as you're facing the lens, the short lead being the emitter of the transistor.		**Phototransistor, infrared (~$0.15). I use a Lite-On LTR-301, which has a red dot to identify itself as a receiver. The collector is the long lead, on the right as you're facing the lens, the short lead being the emitter of the transistor.
	**Switching transistor, 2N2222 or equivalent NPN (~$0.10). I use an R3309, whose leads are emitter, collector, and base, left to right, as seen leading down when looking at the flat face.		**Switching transistor, 2N2222 or equivalent NPN (~$0.10). I use an R3309, whose leads are emitter, collector, and base, left to right, as seen leading down when looking at the flat face.

← Older revision		Revision as of 10:04, 23 April 2025
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	See more discussion and other circuits at [[Circuits for teaching physics]].		See more discussion and other circuits at [[Circuits for teaching physics]].

	For a discussion of the circuit around the photo-transistor, read ''An Arduino-Controlled Photogate'' by Calin Galeriu of Becker College, Worcester, Massachusetts, in The Physics Teacher, v51:n3:pp156-158. ~~http~~://~~dx.~~doi.org/10.1119/1.4792011		For a discussion of the circuit around the photo-transistor, read ''An Arduino-Controlled Photogate'' by Calin Galeriu of Becker College, Worcester, Massachusetts, in The Physics Teacher, v51:n3:pp156-158. https://doi.org/10.1119/1.4792011

	[[Category:Electronics]]		[[Category:Electronics]]