IR detector

[geckogrotto]

Hi all I'm really new to picbasic and to electronics in general.
So please don't be too harsh on me.

I bought this
http://www.radioshack.com/product/in...entPage=search

Here is the back of the package should give more info


What I want to do is basically start a timer when the beam is broken and count every time the beam is broken till its broken 100 times then report back the time.

Lets start with the basics.

So far I have 9V in to a 510 Ohm resistor to the IR led then to ground.
Across from that I have 9V to 10K resistor to the collector side and emitter side to ground.
(connecting a led in series I have been able to get the led to light when the beam is broken
What I'm not sure how to do is get a signal off the detector to a 16F628A input so when the beam is broken I can detect it.

Anyone offer any assistance?

[BobK]

Hello Geckogrotto,

Well you're almost there. First you will need to get a 5 volt regulator to drop your 9 volts down to 5 volts for the PIC. Then connect the 10K resistor between 5 volts and the collector of the phototransistor. You can then connect the junction of the 10K resistor and the collector to the input of your PIC. Your program should "see" a low (ground) condition when the "beam" is being detected and a high (5volts) when the beam is broken.

Hope this helps you!

BobK

[geckogrotto]

Thanks for the help Bob. Like I said im really new to electronics even but is there a way to use resistors instead of a voltage regulator?

[geckogrotto]

WOOT Thanks again Bob I dropped the voltage down to like 4.5V using 3AA batteries instead of a 9V, reduced the resistor on the LED and connected like you said... It works perfect! thanks I would like to know if there is a way with resistors to do the same thing and use a 9v if possible.

[malc-c]

You could use a 5.1v zenner diode to reduce the 9v down to 5v, but a small 5v regulator should be a better bet.

[geckogrotto]

I guess this is where I get confused with electronics.
I can take a 9V battery and use a resistor to run a 1.5V led without problem but I can't use a resistor the same way to run a 5V chip.

This seems to make sense to everyone but me lol

Ok on to the coding would this chip be able to handle the timer part of this or would I need a dedicated timer chip?

My guess is that there will be about 100 breaks in the beam in a 30 second time.

Currently I'm testing with this code and a led on RB1.
Main:
if PORTB.0 = 1 then
high PORTB.1
else
low PORTB.1
endif


Now that looks like it will work fine but, if the loop happens more than once before the bean is brought back it could count 10 times for every break...

Would this code work and only count once?

broken var byte
broken = 0
Main:
if PORTB.0 = 1 and broken = 0 then
broken = 1
high PORTB.1
else
low PORTB.1
endif
if PORTB.0 = 0 and broken = 1 then broken = 0

goto Main

[peterdeco1]

Hi geckogrotto. Try something like this.
START:
LET BROKEN = 0
LOW PORTB.1

Main:
IF PORTB.0 = 1 then ACTIVATE 'BEAM BROKEN
GOTO MAIN 'BEAM NOT BROKEN

ACTIVATE:
IF PORTB.0 = 1 THEN ACTIVATE 'WAIT FOR BEAM TO RETURN
LET BROKEN = BROKEN + 1
IF BROKEN >= 10 THEN LIGHTUP 'BEAM NEEDS TO BE BROKEN 10 TIMES
GOTO MAIN

LIGHTUP:
HIGH PORTB.1
GOTO LIGHTUP

[geckogrotto]

Thanks for your suggestion.

Can anyone tell me how to turn on a timer then turn it off and get the amount of time that was timed?

[Archangel]

Hi, yes you can reduce the voltage to any set level you choose.
Using Ohm's Law
V. out = V in X (r2 / r1 + r2)

where r1 is the resistor closest to the power in
and r2 is the resistor closest to ground

Example v out = v in or 10 volts X r2, say 500 ohms . . . 5000
divided by r2 + r1, so if r1= 500 ohms you would get 1000 ohms,
so 5000 / 1000 = 5 volts. Simple huh? The problem here is if you lose the ground
foe even an instant then your input sees full supply voltage, also a voltage divider uses power all the time, in this example .01 amp.
OK the attachment didn't work so basicly two resistors in series, one end attached to + and the otherend to minus and you pull power from the connection in the center.

[geckogrotto]

Hi, yes you can reduce the voltage to any set level you choose.
Using Ohm's Law
V. out = V in X (r2 / r1 + r2)

where r1 is the resistor closest to the power in
and r2 is the resistor closest to ground

Example v out = v in or 10 volts X r2, say 500 ohms . . . 5000
divided by r2 + r1, so if r1= 500 ohms you would get 1000 ohms,
so 5000 / 1000 = 5 volts. Simple huh? The problem here is if you lose the ground
foe even an instant then your input sees full supply voltage, also a voltage divider uses power all the time, in this example .01 amp.
OK the attachment didn't work so basicly two resistors in series, one end attached to + and the otherend to minus and you pull power from the connection in the center.

Ok I don't think these actually exist but lets say they do.

If I had exactly 9V in and used
R2 950
R1 760
That would give me exactly 5V out?

About the connection what your saying is resistor to + and the other resistor connected to that and then to the negative and sandwiched in between the 2 would be my output of 5v?

Also if you want shoot me over the attachment to [email protected]

Thanks

[Archangel]

That is correct as would 400/500 (notice it adds up to 900) or any variant of above say 1200 /1500 12k/15k what changes as you go upscale is the circuit impeadance (the ability to load the circuit without significant loss of voltage).
If you only want to drive a PIC input pin and not light leds or run motors then use the larger (higher resistance) resistors, that way if you mess up your code and cause an input to become an output, set to low, you will not create a big short.

[geckogrotto]

Thanks again Joe.

Now I just need the most basic code I can find to start / stop the timer and get the results and I will be able to finish the rest.

I searched around the forums but I'm not sure how to implement the code with my chip.

There are internal timers right that you can turn on or off or am I thinking this whole thing wrong and I need to figure out how fast the chip is running then make my own count loop?

[mister_e]

one way in my mind now... Use HPWM on your led emitter, place the IR receiver on RA.4/T0CKI. Use Timer0 to count, Timer1 or Pause to do your sample time. The read the TMR0 register.

Another wich i don't really like but i saw many times... Led emitter directly to Battery via resistor, IR detector to RA.4/T0CKI. Jump in a interupt routine on a TMR0 overflow. Easy neat... may kill the IR Led soon.. battery too.

Do a search for T0CKI, you should find some tips to begin.

[sayzer]

Here is a table again to select a resistor value with respect to current (mA) vs input volt.
Make the rounding as close as possible.



--------

I(mA)	R (ohm)	R (ohm)
	9V	12V

1	9000	12000
2	4500	6000
3	3000	4000
4	2250	3000
5	1800	2400
6	1500	2000
7	1286	1714
8	1125	1500
9	1000	1333
10	900	1200
11	818	1091
12	750	1000
13	692	923
14	643	857
15	600	800
16	563	750
17	529	706
18	500	667
19	474	632
20	450	600
21	429	571
22	409	545
23	391	522
24	375	500
25	360	480
26	346	462
27	333	444
28	321	429
29	310	414
30	300	400
31	290	387
32	281	375
33	273	364
34	265	353
35	257	343
36	250	333
37	243	324
38	237	316
39	231	308
40	225	300
41	220	293
42	214	286
43	209	279
44	205	273
45	200	267
46	196	261
47	191	255
48	188	250
49	184	245
50	180	240
51	176	235
52	173	231
53	170	226
54	167	222
55	164	218
56	161	214
57	158	211
58	155	207
59	153	203
60	150	200
61	148	197
62	145	194
63	143	190
64	141	188
65	138	185
66	136	182
67	134	179
68	132	176
69	130	174
70	129	171
71	127	169
72	125	167
73	123	164
74	122	162
75	120	160
76	118	158
77	117	156
78	115	154
79	114	152
80	113	150
81	111	148
82	110	146
83	108	145
84	107	143
85	106	141
86	105	140
87	103	138
88	102	136
89	101	135
90	100	133
91	99	132
92	98	130
93	97	129
94	96	128
95	95	126
96	94	125
97	93	124
98	92	122
99	91	121
100	90	120
101	89	119
102	88	118
103	87	117
104	87	115
105	86	114
106	85	113
107	84	112
108	83	111
109	83	110
110	82	109
111	81	108
112	80	107
113	80	106
114	79	105
115	78	104
116	78	103
117	77	103
118	76	102
119	76	101
120	75	100
121	74	99
122	74	98
123	73	98
124	73	97
125	72	96
126	71	95
127	71	94
128	70	94
129	70	93
130	69	92
131	69	92
132	68	91
133	68	90
134	67	90
135	67	89
136	66	88
137	66	88
138	65	87
139	65	86
140	64	86
141	64	85
142	63	85
143	63	84
144	63	83
145	62	83
146	62	82
147	61	82
148	61	81
149	60	81
150	60	80


Sayzer August'06
Selecting resistor value with respect to 
Current vs input Volt

[geckogrotto]

After some searching I found this
http://www.picbasic.co.uk/forum/showthread.php?t=190

after making some changes I think I will be able to use this to do what im needing.

[geckogrotto]

Due to all the help I have gotten here I have everything worked out. I decided to buy a lcd screen so I could output the results to it but I have no idea how to hook it up.

LCD Display 16 characters with 2 rows LCD its Hitachi HD44780 compatible LSI controller

It has 16 pins.
1 GND Ground
2 +5v Power
3 Vcont Contrast voltage
4 RS Select
5 R/W Read/Write
6 EN Enable
7 DB0 Data bus
8-14 .......
15 LED K Backlight cathode
16 LED A Backlight anode

Ok 1 and 2 are pretty simple
Im not sure what pins I would hook up to my 16F628A chip. just data bus?
going to do some searching around to see what I can find was just so excited had to post Any help would be appreciated.

[geckogrotto]

Ok looks like mine is almost exactly like the olympic timer
http://www.picbasic.co.uk/forum/atta...4&d=1091819883

So it looks like 7-10 should be data..?

Man I still have so much to learn

[mister_e]

I decided to buy a lcd screen so I could output the results to it but I have no idea how to hook it up.

Free schematic in PBP manual in the LCDOUT section.

[geckogrotto]

Free schematic in PBP manual in the LCDOUT section.

Thanks lol
Good old fashion case of RTFM!

I have one questions about it tho, pin 3 on the lcd connects to the middle of the 20K resistor? I don't understand that part.

also I don't have a 20K resistor should I use 18K , 22K , 18K and 2K in series, or wait till I can get a 20K?

Thanks

[mister_e]

It's a 20K potentiometer or trimmer. It's there to adjust the LCD contrast. You can use lower value. 1-10K still work. You can also use two resistor to make a fix contrast. Wich value... ARRRGGH close to be impossible to tell, no lcd work the same way.

You can still use HPWM to make a software controlled LCD contrast... for now, just plug-it and display on it.
http://www.picbasic.co.uk/forum/show...light=contrast

[geckogrotto]

Got it thanks

[geckogrotto]

Ok last question

I have read all over about floating points and I still can't figure out how to do this.

My calculation is

shotspersecond = count / seconds
shotsperminute = shotspersecond * 60

with floating points this would work fine and tell me shots per minute avg.

Without FP if the seconds > count then I get 0 as shotspersecond and a number of other problems.

I know this can't be too hard but I can't seem to wrap my brain around it.


Any help would be very appriciated as once I get this I should be able to finish off my project.

Any help would be very appriciated as once I get this I should be able to finish off my project.

This is what I have so far... It may be accurate enough for what I am doing.
SPS = 5 / TotalTime
if sps = 0 then
SPS = 5 // TotalTime
SPM = sps * 60 / 100
else
SPM = SPS * 60
endif

Better way to do it?

[SteveB]

My calculation is

shotspersecond = count / seconds

a) Declare your variables as WORDS

b) Multiply count by something like 100 or 1000. This shifts the decimal place to the right. Pick a multiplier that will keep the result below 65536.

b) Now, do the divide: shotspersecond = count / seconds.

c) Display shotspersecond with something like:

LCDOUT DEC shotspersecond/100, ".",DEC2 shotspersecond//100

The key is to shift the decimal place prior to the division, then adjust the display to account for the shift.

For more reading (and a better example of integer math), take a look at These threads from Darrel Taylor:
Retrieving 32bit Multiply Result
Retrieving Div32 Remainder
32-bit Variables and DIV32, Hourmeter 99999.9.

You might also try a search for integer math.

HTH,
Steve

[geckogrotto]

Ohhh thanks Steve I was multiplying x 100 after the divide not before thanks I got it now

[geckogrotto]

Ok really this time last question. This has more to do with eagle but figured you guys would know.
I'm trying to find a LCD like the one on page 94 in the manual to use with eagle and I can't seem to find one.

I downloaded all the LBR files I could find that said LCD on them but still no luck.

[malc-c]

Mat,

Just select one of the connectors / Pin Headers that suit the number of connections on the LCD. This will allow you to either plug the LCD into your board if you use a suitable pin and header block, or solder wires directly to the pads if the LCD is remote from the board

[geckogrotto]

Thanks malc that will work fine.
For anyone who was interested or helped with the process and wanted to see the end result here is a video.

http://www.gecko-grotto.com/workshop/lcd_counter.wmv

[emavil]

Hi, i'm building a simple remote controlled project consisting of 8 12v Relays. I'm using TSOP1738 IR receiver from Vishay Telefunken. I'm using PIC16F84A microcontroller and PICBasic Compiler. I got it from a junked VCD player. Is there anyone who knows how to intercept the coded signal from any IR transmitter? How do i control individual relays independently.

[mister_e]

look at those links
http://rentron.com/PicBasic1.htm
http://rentron.com/remote.htm
http://www.winpicprog.co.uk/pic_tutorial5.htm
Enjoy and good luck!