QUAD-IR

Derived from the Hector design by Bryan Knight and Pete Brownlow, to whom due credit is acknowledged. This version uses a small ARM processor (the so called 32-bits for 32 cents processor), which allowed 4 inputs over the original 2 inputs. A consequence of this is that the circuit voltage is reduced from 5V to 3.3V, requiring the use of low voltage op-amps. The circuit works by taking a reading of the IR level with the IR LED turned off, then takes a reading when turned on. If it's above the sense threshold the output is pulled low for that detector. If it then goes below the sense threshold a small amount of debouncing is applied before turning the output high.

There are a couple of other changes from the original design: The IR LED current is sourced from the input supply rather than the regulated 3.3V; only occupied outputs are available and these are 3.3V push-pull logic levels, with occupied indicated by a low output; supply voltage can be in the range 4.5V-12V. Finally, then on board status led shows the detection without any debouncing, rather than a logical “or” of the outputs.

Pin Functions

The pin functions are:

Pin	Function	Type	Description
1	BOOT0	I/P	Tied to ground
2	PF0	I/O	(IN) Device Enable
3	PF1	I/O	(OUT) Detect 4 Output
4	NRST	RST	SWD - RST
5	VDDA	S	3.3v power supply
6	PA0	I/0	(OUT) Detect 3 Output
7	PA1	I/0	Not Used
8	PA2	I/0	(Analog) Sense Threshold
9	PA3	I/0	(Analog) Sense from Head 4
10	PA4	I/0	(Analog) Sense from Head 3
11	PA5	I/0	(Analog) Sense from Head 2
12	PA6	I/0	(Analog) Sense from Head 1
13	PA7	I/0	(OUT) IR LED Enable
14	PB1	I/0	(OUT) LED Status
15	VSS	S	Ground
16	VDD	S	3.3v power supply
17	PA9	I/0	(OUT) Detect 2 Output
18	PA10	I/0	(OUT) Detect 1 Output
19	PA13	I/0	SWD - SWDIO
20	PA14	I/0	SWD - SWCLK

Other notable ICs

Other notable IC's on the board

Device	Description
LMV324	Quad Low-Voltage Rail-to-Rail Output Operational Amplifier

Schematic

Click on the image above for a PDF version.

Board Layout

The top of the board.

The bottom of the board.