Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

0-5V compass reference

Status
Not open for further replies.
D

DrWhoF

Advanced Member level 1
Advanced Member level 1
Joined
May 6, 2005
Messages
402
Helped
24
Reputation
48
Reaction score
11
Trophy points
1,298
Activity points
4,388
picaxe compass

I have to design a device which takes two 0-5V signals: one comes from 0-360° compass (reference) and one comes from an instrument from inside a tube.
Tube's heading is from the compass and instument's heading has to be calculated with reference to the compass and output as ASCII via serial port.
I need A/D conversion and then some maths to calculate true heading of the instrument.
Any help is highly appreciated.
DrWho
:D
 

If you are happy with 10-bit conversion, you can do it with PICAXE-08M, which has three 10-bit A/D and serial port ..

Compass: 0-359deg <=> 0-5Vdc <=> 0-1023
Instrument: 0-359deg <=> 0-5Vdc <=> 0-1023

The absolute heading of the instrument can be calculated in the following way:

If [Compass] ≤ [Instrument] then [Result] = [Instrument] – [Compass]
If [Compass] > [Instrument] then [Result] = 1023 – ([Compass] – [Instrument])

To output [Resullt] in 0°-359° range you will have to multiply it by 360 and divide it by 1024, but in the PICAXE-BASIC this should not be a problem ..

Rgds,
IanP
 

    D

    DrWhoF

    Points: 2
    Helpful Answer Positive Rating
Hi Ianp.
I don't have picaxe-08m but I have picaxe-18.
Can I use it and can you come up with some picaxe-basic code :cry:
Thanks
:D
 

Try thie code:

Code: 
' Micro: PICAXE-08M or PICAXE-18X
' input  1 [pin6] compass as reference [Ref]
' input  2 [pin5] encoder as instrument [Instr]

		setfreq m8					' serial speed 9600bps ..

start:
		readadc10 1, w0				' Compass as reference => Ref to w0
		readadc10 2, w1				' Encoder as instrument => Instr to w1

		if w0<=w1 then case1			' Res = Instr - Ref
		if w0>w1 then case2			' Res = 360 - (Ref - Instr)
		goto start

	case1:
		w2 = w1 - w0
		goto calc

	case2:
		w2 = 1023 - w0 + w1			' 0/359 => 0/1023 .. with 10-bit adc ..

	calc:
		w3 = w2 * 30				' 12 * 30 = 360
		w3 = w3 / 32				' 32 * 32 = 1024
		w3 = w3 * 12
		w4 = w3 / 32


		sertxd (#w4,$0D,$0A)			' send w4 as ASCII [#w4] 
								' string format: [w4 CR LF]
		pause 1000					' wait 1sec
	goto start

end

Should work with PICAXE-08M [8-pin] and, if you select the right inputs, with PICAXE-18X[18-pin] ..

Rgds,
IanP
 

    D

    DrWhoF

    Points: 2
    Helpful Answer Positive Rating
I will test it on Monday.
thx
:|
 

It is working fine but there is small problem when the instrument's potentiometer is between 5V and 0V (continous rotation): the reading can be anything between 0 and 359deg.
How can this be rectified?
DrWho
 


    D

    DrWhoF

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top