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by PiGraham
Wed Jun 26, 2019 9:02 am
Forum: General discussion
Topic: The RPi4 makes no sense to me. Fight me!
Replies: 30
Views: 1488

Re: The RPi4 makes no sense to me. Fight me!

I have always considered the Raspberry Pi as a platform for embedded systems, with using it as a generic computer being only a fringe application. That isn't the core mission for RPI. It was created for education above all. Enter the RPi4. Dual 4K monitors? USB3? Does someone who can afford the dua...
by PiGraham
Tue Jun 25, 2019 12:14 pm
Forum: General discussion
Topic: Getting IP from headless RPi
Replies: 25
Views: 959

Re: Getting IP from headless RPi

Put both networks in wpa_supplicant.conf and the Pi should automatically connect at home and at school. But the problem is that I dont have access to the school network settings and I cant count on getting them. The solution the school-tech-guys provided was putting all 90 pi-mac-adresses into thei...
by PiGraham
Tue Jun 25, 2019 8:49 am
Forum: General discussion
Topic: Getting IP from headless RPi
Replies: 25
Views: 959

Re: Getting IP from headless RPi

But the fact that the pies get their ip from the school network from the router having their mac-adresses is something I cant change. I understand that having both the school-network and the students home-network in the wpa_supplicant-file would be ideal, but I cant do that. Is it possible to have ...
by PiGraham
Wed Jun 19, 2019 10:04 am
Forum: General discussion
Topic: Using RasPi for multiple display outputs
Replies: 13
Views: 466

Re: Using RasPi for multiple display outputs

Although a Pi per display sounds like overkill, with the Pi0WH its still only $14 or so per display, which is insignificant compared to the development time or having to buy HDMI splitters. It's probably still insignificant with the Pi3B+ at $35!! Since this seems to be for business purposes I shou...
by PiGraham
Wed Jun 19, 2019 9:24 am
Forum: General discussion
Topic: Using RasPi for multiple display outputs
Replies: 13
Views: 466

Re: Using RasPi for multiple display outputs

A useful search phrase is digital signage. There are various projects using RPi. Typically use one Pi per display and feed them over a network. Pi 3A+ might be a good choice for the per-display units. You can duplicate one HDMI to multiple screens so all display the same image. You can use USB displ...
by PiGraham
Mon Jun 17, 2019 3:02 pm
Forum: General discussion
Topic: Generate multiple PWM signals
Replies: 5
Views: 202

Re: Generate multiple PWM signals

For PWM motor control I would like to have continuous frequency. While pigpio library is really cool (I use it a lot here: https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter ), software PWM frequencies are too restricted: http://abyz.me.uk/rpi/pigpio/pigs.html#PFS I'm curious...
by PiGraham
Fri Jun 14, 2019 1:56 pm
Forum: C/C++
Topic: Camera Image Annotate Position
Replies: 1
Views: 152

Re: Camera Image Annotate Position

How about
MMAL_PARAMETER_CAMERA_ANNOTATE_V4_T

Code: Select all

  uint32_t    justify; //0=centre, 1=left, 2=right

   uint32_t    x_offset; //Offset from the justification edge

   uint32_t    y_offset;

https://github.com/raspberrypi/userland ... s_camera.h
by PiGraham
Fri Jun 07, 2019 7:55 am
Forum: General discussion
Topic: light detector with photo transistor
Replies: 33
Views: 1034

Re: light detector with photo transistor

I have tried the cicrcuit with 100K resistor and exposing it to the camera flashlight but it is giving max 400mV. So it is definitely responding to light level then? Yes it is responding to light level but not to that smd led from the chip. How are you positioning the LED and phototransistor? Does ...
by PiGraham
Fri Jun 07, 2019 7:51 am
Forum: General discussion
Topic: How many 2.5" drives?
Replies: 19
Views: 625

Re: How many 2.5" drives?

You should try to test a maximum load condition. Four drives all spinning up at once and moving the heads at the same time could be very different to 3 drives idling and one active. Make sure you don't loose drives at moments of peak power demand. Your best option for power distribution is probably ...
by PiGraham
Thu Jun 06, 2019 1:33 pm
Forum: General discussion
Topic: light detector with photo transistor
Replies: 33
Views: 1034

Re: light detector with photo transistor

rajbuddy007 wrote:
Thu Jun 06, 2019 12:43 pm

I have tried the cicrcuit with 100K resistor and exposing it to the camera flashlight but it is giving max 400mV.
So it is definitely responding to light level then?
by PiGraham
Thu Jun 06, 2019 12:11 pm
Forum: General discussion
Topic: light detector with photo transistor
Replies: 33
Views: 1034

Re: light detector with photo transistor

Data for the LED shows luminous intensity of 110mcd This calculator shows an illuminance of 27500lx at 2mm using 0.110 candela and 0.002m and 1100lx at 10mm if we just assume an isotropic radiation pattern. So you should have planty of light from the LED to operate the sensor if you aim them right a...
by PiGraham
Thu Jun 06, 2019 11:57 am
Forum: General discussion
Topic: light detector with photo transistor
Replies: 33
Views: 1034

Re: light detector with photo transistor

I dont think it will give desired output for the light which i have to detect. Please check the datasheet of the smd led. Should i use comparator for it? SMD LED https://www.mouser.de/datasheet/2/216/APTD1608LSURCK-1102303.pdf Before you do anything else make sure the sensor actually works. You sho...
by PiGraham
Thu Jun 06, 2019 11:08 am
Forum: General discussion
Topic: light detector with photo transistor
Replies: 33
Views: 1034

Re: light detector with photo transistor

The spec says Collector light current 200uA at 5V and 200lx illuminance, 70uA at 20 lx so you could expect 200uA in a bright daylit room, maybe <=100uA in the dark room in your photo. https://en.wikipedia.org/wiki/Illuminance#Common_illuminance_levels So connected as pcmanbob's circuit with a 10k pu...
by PiGraham
Wed Jun 05, 2019 8:11 am
Forum: General discussion
Topic: light detector with photo transistor
Replies: 33
Views: 1034

Re: light detector with photo transistor

Please help . We have helped. I gave you a link to a tutorial for using an optoisolator with RPi that shows the connections for a phototransistor. Burngate gave you useful suggestions for adapting to your specific use. The code is like code for any digital gpio input like a button or a sensor. Try ...
by PiGraham
Tue Jun 04, 2019 3:18 pm
Forum: Automation, sensing and robotics
Topic: RS-232C Terminal to remotely control receiver volume. Can I do that?
Replies: 5
Views: 166

Re: RS-232C Terminal to remotely control receiver volume. Can I do that?

mikronauts wrote:
Tue Jun 04, 2019 3:03 pm
You could also use an ir led and lirc.

That is a great suggestion if you have a remote controll you can scan to read volume commands because you don't need to find possibly obscure doccumentation.
by PiGraham
Tue Jun 04, 2019 3:15 pm
Forum: Automation, sensing and robotics
Topic: RS-232C Terminal to remotely control receiver volume. Can I do that?
Replies: 5
Views: 166

Re: RS-232C Terminal to remotely control receiver volume. Can I do that?

Hi, guys, I'm wondering if there is a way to remotely control the volume on my stereo receiver using a raspberry pi connected to the receiver's RS-232C terminal. This is mostly a question about your receiever and it's capability to adkjust volume via serial commands. At the very least you would hav...
by PiGraham
Tue Jun 04, 2019 11:04 am
Forum: Automation, sensing and robotics
Topic: Checking when food/water bowls are empty?
Replies: 22
Views: 808

Re: Checking when food/water bowls are empty?

What kind of food will you use? Will it leave the QR clean enough to read reliably, or might food remnants or muddy footprints cause problems? Debris faling into the bowls might also be tricky. The bowls are going to be inside the house, so hopefully debris is not a problem. Was going to use dry bi...
by PiGraham
Tue Jun 04, 2019 10:57 am
Forum: Automation, sensing and robotics
Topic: Checking when food/water bowls are empty?
Replies: 22
Views: 808

Re: Checking when food/water bowls are empty?

What kind of food will you use? Will it leave the QR clean enough to read reliably, or might food remnants or muddy footprints cause problems? Debris faling into the bowls might also be tricky.
by PiGraham
Tue Jun 04, 2019 9:53 am
Forum: General discussion
Topic: light detector with photo transistor
Replies: 33
Views: 1034

Re: light detector with photo transistor

Thank for the reply. I want to detect a light from this LED. Please do check and tell me what should be the best practice for it? https://www.mouser.de/datasheet/2/216/APTD1608LSURCK-1102303.pdf Connect it as the phototransitor part of an optoisolator. http://raspberrypihobbyist.blogspot.com/2012/0...
by PiGraham
Tue Jun 04, 2019 8:52 am
Forum: General discussion
Topic: light detector with photo transistor
Replies: 33
Views: 1034

Re: light detector with photo transistor

You may not need a comparator if the the light from the LED is enough to turn the phototransistor on enough to pull a GPIO to a safe on or off level against a pullup, and allow the GPIO to return to the opposite state when the LED is off. If youoptically couple the sensor closely to the LED and excl...
by PiGraham
Tue Jun 04, 2019 8:34 am
Forum: Automation, sensing and robotics
Topic: Checking when food/water bowls are empty?
Replies: 22
Views: 808

Re: Checking when food/water bowls are empty?

Whichever method you choose it may not matter if animals climb into bowls. If the objective is to detect EMPTY bowls then the significant reading is when there is nothing in the bowl. Hedgehogs or rats aren't going to be permanently in the bowls and when they leave you get a reading of whatever is l...
by PiGraham
Sun Jun 02, 2019 8:24 am
Forum: Automation, sensing and robotics
Topic: Self-managing race car air suspension
Replies: 7
Views: 397

Re: Self-managing race car air suspension

I want to try and build an "affordable" system that can actively monitor and adjust air pressure in each of the 4 air-shocks using height as the reference measurement. The plan is to use these shocks https://www.airliftperformance.com/product/82607/ and this encoder https://www.adafruit.com/product...
by PiGraham
Tue May 28, 2019 10:38 am
Forum: Other projects
Topic: georeferencing a voltage
Replies: 5
Views: 1046

Re: georeferencing a voltage

think I might get along faster by programming an android app. where to start with that? (a more experienced friend has advised me that phones are difficult to program) You could check out https://appinventor.mit.edu/explore/ for something easy to get into but I don't know of would be any use for wh...
by PiGraham
Mon May 27, 2019 10:40 am
Forum: Camera board
Topic: Stereo Vision on Raspberry Pi 3B+
Replies: 14
Views: 747

Re: Stereo Vision on Raspberry Pi 3B+

This could be relevant. Maybe you could use RPi compatible ArduCam camera modules with external reset to synchronise two sensors. https://www.raspberrypi.org/forums/viewtopic.php?f=43&t=241418&sid=b02a0a0ccb8f55f99392bd24bb50728e Only if you also have the external strobe lighting required, otherwis...

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