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OA47

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Joined: 11/04/2012
Location: Australia
Posts: 1021

Posted: 05:47am 01 Feb 2026

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Just going through some of the unfinished projects and came across a handheld IR TACHO that I built many years ago. I have very simple code to run this unit but I feel it can be made much more accurate and reliable. Here is the code currently:

' IR TACHOMETER PROGRAM FOR MICROMITE
' IR LED POWERED ON
' IR RECEIVER CONNECTED TO PIN 16

' INITIALISE PINS FOR 2 LINE LCD
LCD INIT 2,3,4,5,23,24

SetPin 16,FIN 'IR RECEIVER
Dim Spin,I

LCD 1,3,"IR TACHOMETER"
LCD 2,10," RPM"
Do
Spin=0
For I = 1 To 10
Spin = Spin + Pin(16)
Next I

Print Spin/10;" Hz"

LCD 2,1,Str$(Spin*6)
Pause 500
LCD 2,1," "
Loop

Has anyone any suggestions to improve this program?

OA47

ville56
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Joined: 08/06/2022
Location: Austria
Posts: 384

Posted: 06:44am 01 Feb 2026

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Tbh, I don't get the program logic at all...

73 de OE1HGA, Gerald

phil99

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Joined: 11/02/2018
Location: Australia
Posts: 2967

Posted: 07:06am 01 Feb 2026

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MM 5.05.05 manual said Counting Inputs
The pins marked as COUNT can be configured as counting inputs to measure frequency, period or just count
pulses on the input.
For example, the following will print the frequency of the signal on pin 15:
> SETPIN 15, FIN
> PRINT PIN(15)
110374
>
In this case the frequency is 110.374 kHz.

Multiply by 60 for RPM.

The one I built uses an IR remote control receiver and the IR LED is fed with a 38kHz 50% PWM output.
This gives it a much better tolerance for high ambient light and works at a greater distance due to the narrow bandwidth, high gain and excellent AGC of the IR receiver.
Tested to 30,000 RPM.
Edited 2026-02-01 17:08 by phil99

Volhout
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Joined: 05/03/2018
Location: Netherlands
Posts: 5656

Posted: 11:18am 01 Feb 2026

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Hi OA47,

remember...

https://www.thebackshed.com/forum/ViewTopic.php?TID=16669&P=2#217359

Volhout

PicomiteVGA PETSCII ROBOTS

OA47

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Joined: 11/04/2012
Location: Australia
Posts: 1021

Posted: 11:33pm 01 Feb 2026

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Volhout, thankyou for bringing that to my attention. Obviously my static brain ram backup battery has faded and I have been down this road before.

OA47

Volhout
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Joined: 05/03/2018
Location: Netherlands
Posts: 5656

Posted: 08:05am 02 Feb 2026

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Hi OA,

You simply picked up again where you left of last time.

Volhout

PicomiteVGA PETSCII ROBOTS

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