I have some vishay sensors and realise now, they need a modulated 38KHz IR beam to work, not just 38KHz as that gives low range detection.
I can't work out the data sheet. Does the IR have to be 8 pulses at 38KHz then 8 no pulses for same time then repeat a few times? https://www.vishay.com/docs/82479/tssp58038.pdf
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Stan,
several years ago i was working on a Vend light curtain and we used 10 cycles of 38khz to check each position.
I see on the timing diagram it also suggests:* tpi 10/f0 is recommended for optimal function.
We used very simple generator
for next 10 cycles
turn IR on
wait 13us
turn ir off
wait 13us
Hope this helps
73
Mike
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trial and error tested before your 13 us suggestion but frequency jumps around on poor scope and think pwm more acurate as the recievers are tuned. Is 38KHz pwm possible?
If I send ten pulses at 38KHz then test the reciever out going low straight away, does it stay low long enough after the IR signal has stopped for it to be tested or would I need a hardware pwm signal?
I'll experiment and see.
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Stan,
Attached is one of the development files from 2008.
It looks like the vishay stays on for a bit after being pumped up. I was
using If statement to detect if the sensor was blocked.
Also note i must have been "tuning" the IR emmitter timing because some of
the array of sensor / emmiters are 13us on and 7 us off for the generator.
Remember this is GCB from 2008 on a linux box using gedit for the IDE. It
worked quite well!
dir portb.0 out
IntOff
do
portb.0=1
;repeat 28
;end repeat
wait 13 us
nop
portb.0=0
;repeat 28
;end repeat
wait 13 us
loop
~~~
trial and error tested before your 13 us suggestion but frequency jumps
around on poor scope and think pwm more acurate as the recievers are tuned.
Is 38KHz pwm possible?
If I send ten pulses at 38KHz then test the reciever out going low
straight away, does it stay low long enough after the IR signal has stopped
for it to be tested or would I need a hardware pwm signal?
I'll experiment and see.
The data sheet says 600us of 38KHz pulses and 600us low. Works fine. This device is fixed high gain and doesn't time out. It's pretty dumb and predictable. I'm trying irled-sensor-irled-sensor-irled-sensor-irled for bobot. ie left,forward,right sensing. I'll get back if it works ok.
Stan, couldn't help but notice this thread on the 38kHz IR sensor. Would you mind testing the GCB hardware PWM for AVR with this device? I know for a fact you will not get exactly 38kHz, but it would be good to know if the Vishay device will work within this tolerance.
'This program demonstrates the PWMOn and PWMOff commands
'of the fixed mode HPWM on OC0B pin.
#chip mega328p,16
'activate appropriate PWM output pins
dir PortD.5 Out 'OC0B
'define PWM_Freq in kHz
#define PWM_Freq 38
'define PWM_Duty in %
#define PWM_Duty 50
Start:
'turn on/off single channel 38 KHz PWM on OC0B pin
PWMON
wait 600 us
PWMOFF
wait 600 us
goto Start
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It didn't work, nor did software 38KHz.
pwm gives 37.74KHz to ir led (unknown-measures 1.1V on diode range and driven through 100R resistor). I can see the ir led is lit in photo (Not visible to eye)
Circuit works if I make pb.0 +- glcd says on for off and off for on
edit done my head hours looking for errors. I read users get range by changing 38KHz +- few hundred Hz. Probably differrent device. I'll test other 3pin ir receivers and this with a sig gen at 38KHz
Stan, I am not exactly sure on your wiring, but the pin diode of the receiver will turn on the internal transistor which I believe will invert the polarity of the output pin. So that part is right?
The data sheet says to block any stray illuminence of the IR led, so try a piece of shrink tube, or something, over the led to cover the sides. Also some ir leds can have a fairly narrow beam, and I notice the alignment of the IR led to the receiver window are not aligned, or in the same plane (i.e. receiver is parallel to the breadboard and the IR led is pointing straight up at 90 deg. Can you bend the led pins 90 deg. so they are in alignment, or pointing in the same direction as the receiver window)?
Here is a link that shows how to hook up an indicator led to the 3 pin receiver module to let you know the status. https://learn.adafruit.com/ir-sensor/testing-an-ir-sensor Also, you can try a remote(s) to see if the receiver output pin will go low.
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If the sensor detects 38KHz the output goes low. I did try moving the sensor and white card to reflect and black card to stop interference as per tubes. tv remotes not detected but I know vishays detect tv remotes well.
The output is high so not reacting to ir. Not swamped I think.
I noticed narrow pulses on the output at half the ir frequency.
I tried another vishay tsop 38438 which is modulated output but couldn't detect.
I have some unknown ir sensors from toys and tv to try. Some I've used with pic but doesn't solve if ir frequency is near enough to 38khz. I'll get back after experiments.
Last edit: stan cartwright 2017-12-23
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It works with different sensor (eaglemoss robot) but these are carp remembering picaxe tests and driving the ir led through a small tranny to get any distance.
So yes, 38KHz pwm works. Note it goes low as a pulse..must scope. https://youtu.be/YTzxPeUw88k
ps tv remotes overdrive the ir leds briefly...it seems.
Last edit: stan cartwright 2017-12-23
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tssop4838 has agc. Does that make it unpredictable? I dunno. What are you going to use it for?
Nano is like uno. Easy to use with gcb and 2K ram. compared to 64meg pic is it same speed as it does instruction every clock but pic is every 4 clock. 328 is 20MHz on arduino but 16MHz on gcb?
anyway nice for 2 quid
ps think about driving the ir led through a transistor for increas reflectance range.
Last edit: stan cartwright 2017-12-23
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gcb pwm 38KHz is 250 below and 39 is 250 above and can't be exact with software so maybe a device tuned to frequency that can be the same with gcb. must be a uctrl thing..clock divs.
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Less than one percent freq. error (at least at 38kHz) seems pretty good, shouldn't have a significant response problem from the IR detector if you follow the chart in the data sheet. Of course some frequencies will be spot on, try 40kHz for instance if my memory serves me correctly.
In the case of the HPWM for AVR, the 8bit TMR0 was used for the PWMON and PWMOFF function because to the best of my knowledge every AVR has one including the Tiny's. And therein begins the process of tradeoffs, as certainately a 16bit TMR1 or the TMR2 with the refined prescaler would be better choices.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
I have some vishay sensors and realise now, they need a modulated 38KHz IR beam to work, not just 38KHz as that gives low range detection.
I can't work out the data sheet. Does the IR have to be 8 pulses at 38KHz then 8 no pulses for same time then repeat a few times? https://www.vishay.com/docs/82479/tssp58038.pdf
Stan,
several years ago i was working on a Vend light curtain and we used 10 cycles of 38khz to check each position.
I see on the timing diagram it also suggests:* tpi 10/f0 is recommended for optimal function.
We used very simple generator
for next 10 cycles
turn IR on
wait 13us
turn ir off
wait 13us
Hope this helps
73
Mike
Thanks Mike. I tried
trial and error tested before your 13 us suggestion but frequency jumps around on poor scope and think pwm more acurate as the recievers are tuned. Is 38KHz pwm possible?
If I send ten pulses at 38KHz then test the reciever out going low straight away, does it stay low long enough after the IR signal has stopped for it to be tested or would I need a hardware pwm signal?
I'll experiment and see.
Stan,
Attached is one of the development files from 2008.
It looks like the vishay stays on for a bit after being pumped up. I was
using If statement to detect if the sensor was blocked.
Also note i must have been "tuning" the IR emmitter timing because some of
the array of sensor / emmiters are 13us on and 7 us off for the generator.
Remember this is GCB from 2008 on a linux box using gedit for the IDE. It
worked quite well!
73
M
On Wed, Dec 20, 2017 at 4:44 PM, stan cartwright stanleyella@users.sf.net
wrote:
--
Mike Otte W9YS
The data sheet says 600us of 38KHz pulses and 600us low. Works fine. This device is fixed high gain and doesn't time out. It's pretty dumb and predictable. I'm trying irled-sensor-irled-sensor-irled-sensor-irled for bobot. ie left,forward,right sensing. I'll get back if it works ok.
Stan, couldn't help but notice this thread on the 38kHz IR sensor. Would you mind testing the GCB hardware PWM for AVR with this device? I know for a fact you will not get exactly 38kHz, but it would be good to know if the Vishay device will work within this tolerance.
It didn't work, nor did software 38KHz.
pwm gives 37.74KHz to ir led (unknown-measures 1.1V on diode range and driven through 100R resistor). I can see the ir led is lit in photo (Not visible to eye)
Circuit works if I make pb.0 +- glcd says on for off and off for on
edit done my head hours looking for errors. I read users get range by changing 38KHz +- few hundred Hz. Probably differrent device. I'll test other 3pin ir receivers and this with a sig gen at 38KHz
Last edit: stan cartwright 2017-12-22
Stan, I am not exactly sure on your wiring, but the pin diode of the receiver will turn on the internal transistor which I believe will invert the polarity of the output pin. So that part is right?
The data sheet says to block any stray illuminence of the IR led, so try a piece of shrink tube, or something, over the led to cover the sides. Also some ir leds can have a fairly narrow beam, and I notice the alignment of the IR led to the receiver window are not aligned, or in the same plane (i.e. receiver is parallel to the breadboard and the IR led is pointing straight up at 90 deg. Can you bend the led pins 90 deg. so they are in alignment, or pointing in the same direction as the receiver window)?
Here is a link that shows how to hook up an indicator led to the 3 pin receiver module to let you know the status. https://learn.adafruit.com/ir-sensor/testing-an-ir-sensor Also, you can try a remote(s) to see if the receiver output pin will go low.
If the sensor detects 38KHz the output goes low. I did try moving the sensor and white card to reflect and black card to stop interference as per tubes. tv remotes not detected but I know vishays detect tv remotes well.
The output is high so not reacting to ir. Not swamped I think.
I noticed narrow pulses on the output at half the ir frequency.
I tried another vishay tsop 38438 which is modulated output but couldn't detect.
I have some unknown ir sensors from toys and tv to try. Some I've used with pic but doesn't solve if ir frequency is near enough to 38khz. I'll get back after experiments.
Last edit: stan cartwright 2017-12-23
It works with different sensor (eaglemoss robot) but these are carp remembering picaxe tests and driving the ir led through a small tranny to get any distance.
So yes, 38KHz pwm works. Note it goes low as a pulse..must scope. https://youtu.be/YTzxPeUw88k
ps tv remotes overdrive the ir leds briefly...it seems.
Last edit: stan cartwright 2017-12-23
OK, good to know. I put a couple of tssop4838's and a Nano on order to play with. Thanks!
tssop4838 has agc. Does that make it unpredictable? I dunno. What are you going to use it for?
Nano is like uno. Easy to use with gcb and 2K ram. compared to 64meg pic is it same speed as it does instruction every clock but pic is every 4 clock. 328 is 20MHz on arduino but 16MHz on gcb?
anyway nice for 2 quid
ps think about driving the ir led through a transistor for increas reflectance range.
Last edit: stan cartwright 2017-12-23
Mostly will use the tssop4838 to try the NEC? protocol or maybe just on/off function. For future reference, or just an excercise for the brain :)
gcb pwm 38KHz is 250 below and 39 is 250 above and can't be exact with software so maybe a device tuned to frequency that can be the same with gcb. must be a uctrl thing..clock divs.
Less than one percent freq. error (at least at 38kHz) seems pretty good, shouldn't have a significant response problem from the IR detector if you follow the chart in the data sheet. Of course some frequencies will be spot on, try 40kHz for instance if my memory serves me correctly.
In the case of the HPWM for AVR, the 8bit TMR0 was used for the PWMON and PWMOFF function because to the best of my knowledge every AVR has one including the Tiny's. And therein begins the process of tradeoffs, as certainately a 16bit TMR1 or the TMR2 with the refined prescaler would be better choices.