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by PiGraham
Sat Nov 09, 2019 10:35 am
Forum: Automation, sensing and robotics
Topic: Distances of two different points in x y z coordinates
Replies: 23
Views: 1919

Re: Distances of two different points in x y z coordinates

If it has to be cheap you could try 2 cameras, probably usb so 2 will work on a pi, and determine the distances to the points, from the difference between the images after you have calibrated. You could then use my earlier method with measured angles. Good point. If two cameras are rigidly mounted ...
by PiGraham
Fri Nov 08, 2019 5:06 pm
Forum: Other projects
Topic: Wireless Distance Sensing?
Replies: 38
Views: 2849

Re: Wireless Distance Sensing?

https://gaorfid.com/product/reader-active-usb-receiver-2-45-ghz-rfid/ 20m range used with active tags https://gaorfid.com/devices/rfid-tags-by-frequencies/active-2-45-ghz-rfid-tags/ Or something from eBay https://www.ebay.co.uk/itm/Active-RFID-Electronic-Tag-Reader-Undervoltage-reminder-ABS-For-Navi...
by PiGraham
Fri Nov 08, 2019 1:53 pm
Forum: Automation, sensing and robotics
Topic: Distances of two different points in x y z coordinates
Replies: 23
Views: 1919

Re: Distances of two different points in x y z coordinates

I don't think ". I have no restrictions on that device." means "money no object".

Still, this is cool if can afford it. Measure whatever you want.

https://www.youtube.com/watch?v=KUdbrFOJlO0

Or

https://www.youtube.com/watch?v=aq4NLmiJHwk
by PiGraham
Fri Nov 08, 2019 11:22 am
Forum: Other projects
Topic: Wireless Distance Sensing?
Replies: 38
Views: 2849

Re: Wireless Distance Sensing?

This claims to be BT5.0 Eddystone beacon in a watch format. 1 yr battery life
https://www.amazon.co.uk/JINOU-OEM-Prog ... B07HQ9DJKG
by PiGraham
Fri Nov 08, 2019 11:19 am
Forum: Other projects
Topic: Wireless Distance Sensing?
Replies: 38
Views: 2849

Re: Wireless Distance Sensing?

But the new BT5.1 is supposed to do this. Nordic's nRF52811 is one of the first chips, but I have yet to see usable positioning solutions for hackers. This could change any month or week. That's exciting tech. Sub 1m accuracy with direction and elevation. https://www.youtube.com/watch?v=c3XqbEKmNcM
by PiGraham
Fri Nov 08, 2019 9:13 am
Forum: Other projects
Topic: Wireless Distance Sensing?
Replies: 38
Views: 2849

Re: Wireless Distance Sensing?

Not surprisingly there are a lot of phone apps claiming to "locate your Bluetooth devices" I tried a couple but they don't seem effective. The reported signal strength doesn't vary with distance in a consistent way. I used a Bluetooth speaker that was not connected. That means it keeps advertising i...
by PiGraham
Fri Nov 08, 2019 7:58 am
Forum: Automation, sensing and robotics
Topic: Distances of two different points in x y z coordinates
Replies: 23
Views: 1919

Re: Distances of two different points in x y z coordinates

You still haven't indicated what sort of accuracy you need for this measurement. That's critical.
The other key parameter is what distances you need to measure.

You can measure anything with triangulation, so long as you have at least one known distance.
by PiGraham
Thu Nov 07, 2019 5:51 pm
Forum: Troubleshooting
Topic: RPi Internal Pull-Up Resistors Not Functioning
Replies: 11
Views: 402

Re: RPi Internal Pull-Up Resistors Not Functioning

What do you see if you just poll the input and print the state and press the button?

Code: Select all

mport RPi.GPIO as GPIO
import os
import time

GPIO.setmode(GPIO.BCM)

GPIO.setup(21, GPIO.IN, pull_up_down=GPIO.PUD_UP)

while(True):
	print (GPIO.input(21))
	time.sleep(0.1)
	
by PiGraham
Thu Nov 07, 2019 3:12 pm
Forum: General discussion
Topic: GPIOs working in parallel
Replies: 5
Views: 489

Re: GPIOs working in parallel

Hello, Can I have different GPIOs working in parallel. For example can I have GPIO 17 -----> working as input GIPO 27 -----> working as input GPIO 22 -----> working as output at the same code? and nearly at the same time? You can certainly set au gpios as a mix of inputs and outputs. What do you me...
by PiGraham
Wed Nov 06, 2019 11:28 pm
Forum: General discussion
Topic: Use GPIO for PWM in "open collector mode" ?
Replies: 5
Views: 811

Re: Use GPIO for PWM in "open collector mode" ?

Thanks! Sounds good! So "open collector" is a term that refers to switching via (another) transistor? Not it means the collector of the output transistor is not tied to another transistor or a pullup to a voltage rail. That it is, the collector is free to float at any applied voltage when the trans...
by PiGraham
Wed Nov 06, 2019 5:54 pm
Forum: Automation, sensing and robotics
Topic: Distances of two different points in x y z coordinates
Replies: 23
Views: 1919

Re: Distances of two different points in x y z coordinates

Actually, its probably a reasonable assumption that the walls are vertical so a horizontal sweep of a distance sensor of any type could give you the walls and a range straight up could give the ceiling which gets you the corners. It all depends what accuracy is needed because walls aren't perfectly ...
by PiGraham
Wed Nov 06, 2019 5:50 pm
Forum: Automation, sensing and robotics
Topic: Distances of two different points in x y z coordinates
Replies: 23
Views: 1919

Re: Distances of two different points in x y z coordinates

Park a laser distance sensor on a tripod, adjust its tilt until the laser beam can be swung to hit the two corners. Measure the two distances and use the angle swung to calculate the distance between the two corners. I mentioned two types of laser distance sensor. True it would be a lot simpler to ...
by PiGraham
Wed Nov 06, 2019 3:08 pm
Forum: Automation, sensing and robotics
Topic: Distances of two different points in x y z coordinates
Replies: 23
Views: 1919

Re: Distances of two different points in x y z coordinates

Not a trivial problem. A level or higher mathematics would be useful to understand how these techniques work although you may get through treating libraries as black boxes that give you numbers. You would be relying a lot on examples though. You should start by defining what accuracy you need. Some ...
by PiGraham
Wed Nov 06, 2019 12:52 pm
Forum: Other projects
Topic: Wireless Distance Sensing?
Replies: 38
Views: 2849

Re: Wireless Distance Sensing?

Posyx looks good but expensive in RPi terms.

https://www.pozyx.io/shop
by PiGraham
Wed Nov 06, 2019 9:45 am
Forum: Other projects
Topic: Wireless Distance Sensing?
Replies: 38
Views: 2849

Re: Wireless Distance Sensing?

I'm waiting for someone to make a Bluetooth 5.1 diversity antenna Hat/module. Use RF module and the RSSI feature. Another way is RFID chips and RDF methods, low freq rf transmitter and directional coil antennas. You could put multiple USB BT adaptors on a Pi, arranging antennas in a wide triangle o...
by PiGraham
Tue Nov 05, 2019 7:51 pm
Forum: Other projects
Topic: Wireless Distance Sensing?
Replies: 38
Views: 2849

Re: Wireless Distance Sensing?

I've done some testing with having 2 different HC-SR04, however I don't believe that this route will work, at least not with these specific modules. It seems that as soon as the module has received its echo, it stops listening for more echo's, which puts this part dead in its tracks. You don't have...
by PiGraham
Tue Nov 05, 2019 4:38 pm
Forum: Other projects
Topic: Wireless Distance Sensing?
Replies: 38
Views: 2849

Re: Wireless Distance Sensing?

It sounds like you need battery power and small size. Maybe Pi ZeroW plus a USB power pack but maybe ESP32 or ATTiny which could run on a coin cell for a lot longer than the Pi. For sensing Bluetooth might be an easy option. You could read the RRSI signal strength of each Bluetooth or Wi-Fi device. ...
by PiGraham
Tue Nov 05, 2019 2:02 pm
Forum: General discussion
Topic: Vintage radio tuner
Replies: 19
Views: 1637

Re: Vintage radio tuner

Only 1 project. That's not a constructive attitude. Like I said I'm new to using a pi. So what I'm asking might sound right out to lunch. You are intimidated by the task probably because you can't break it down into manageable chunks. That's sound engineering practice and good advice you don't seem...
by PiGraham
Tue Nov 05, 2019 9:06 am
Forum: General discussion
Topic: Vintage radio tuner
Replies: 19
Views: 1637

Re: Vintage radio tuner

So there are some multiple projects here: 1 add Bluetooth and MP3 functions to an old radio cassette (Pi or BT board audio out. Maybe mod radio for line in ) 2. Add some sort of digital remote controllable tuning mechanism to turn the analog dial of an old radio cassette (stepper motor drive) 3. Add...
by PiGraham
Mon Nov 04, 2019 10:42 pm
Forum: General discussion
Topic: Vintage radio tuner
Replies: 19
Views: 1637

Re: Vintage radio tuner

So we still don't know what you mean by "have the original tuner choose the station. So if I had an fm radio on my rpi and I used the dial to tune in the channels. Instead of a digital display to choose the station But you have an fm radio with a dial to tune in the stations, right? And you want to...
by PiGraham
Mon Nov 04, 2019 8:18 pm
Forum: General discussion
Topic: Vintage radio tuner
Replies: 19
Views: 1637

Re: Vintage radio tuner

So I'm kinda new to this but I want to refurbish on old style radio with the dial tuner for the radio. Question is there a way to connect it to a pi? I mean with volumio and have the original tuner used to choose the station? Basically I want to rebuild an old radio cassette player and keep everyth...
by PiGraham
Mon Nov 04, 2019 6:35 pm
Forum: General discussion
Topic: Use GPIO for PWM in "open collector mode" ?
Replies: 5
Views: 811

Re: Use GPIO for PWM in "open collector mode" ?

You can't connect RPi gpio like that. The LED supply voltage is almost certainly too high for a Pi (3.3V) You could add a second transistor like Q1. Lets call it Q3. Connect collector to collector and emitter to emitter. Drive the base from your gpio output through a 100 ohm resistor. When the GPIO ...
by PiGraham
Mon Nov 04, 2019 3:54 pm
Forum: General discussion
Topic: Vintage radio tuner
Replies: 19
Views: 1637

Re: Vintage radio tuner

To read the dial position you need an absolute position sensing device. You could use a potentiometer and an analogue to digital converter (ADC) or some sort of absolute optical encoder. Maybe something like this https://uk.farnell.com/bourns/eaw0j-b24-ae0128l/encoder-rotary-128pos-8-bit/dp/9358234?...
by PiGraham
Mon Nov 04, 2019 3:50 pm
Forum: General discussion
Topic: Vintage radio tuner
Replies: 19
Views: 1637

Re: Vintage radio tuner

You could use an encoder in place of the tuner dial to recognise clockwise/anti clockwise turns. https://thepihut.com/products/keyes-rotary-encoder-module Haven't used volumio, not sure what that can accept. I like the encoder idea. But would the station I'm tuning correspond with the one shown on ...
by PiGraham
Mon Nov 04, 2019 9:29 am
Forum: Other projects
Topic: smooth analog voltage from 0 to 12V
Replies: 10
Views: 1479

Re: smooth analog voltage from 0 to 12V

Mind you, if you have a strip of 60 LEDs you could illuminate some fraction of them. If you can diffuse the light well enough you could light one of the 60 at lowest levent, up to all 60 at highest level. 1/256 * 1/60 = 1/15,360 or about 14 bits equivalent. It's probably difficult to spread the ligh...

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