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by PiGraham
Fri May 24, 2019 5:49 pm
Forum: Camera board
Topic: Stereo Vision on Raspberry Pi 3B+
Replies: 4
Views: 88

Re: Stereo Vision on Raspberry Pi 3B+

As I know at the moment, there are two solutions for my current problem. I want to take a pair of images from two pi camera at the same time in order to do stereo vision. 1. The first solution is to use two separate Pi Compute board and 2 separate Pi camera for each board and to use GStreamer. 2. T...
by PiGraham
Thu May 23, 2019 3:54 pm
Forum: Automation, sensing and robotics
Topic: need super small PIR sensor
Replies: 13
Views: 227

Re: need super small PIR sensor

For a mirror you may be able to use the PIR without the dome. The dome gives the sensor a wide area coverage but the senor itself is small. You may find it triggers OK without the dome if you move directly in front of it. That's probably OK for a mirror unless you want the system to boot up as soon ...
by PiGraham
Thu May 23, 2019 2:39 pm
Forum: Automation, sensing and robotics
Topic: Checking when food/water bowls are empty?
Replies: 14
Views: 222

Re: Checking when food/water bowls are empty?

Weight is the obvious choice and probably the most direct way to measure what you wan't to know. Still, other techniques might be useful. You could try ultrasonic or IR distance sensors to see if they will read off the surface of the food you use. If so then you can zero the distance on empty bowls ...
by PiGraham
Thu May 23, 2019 1:58 pm
Forum: Other projects
Topic: georeferencing a voltage
Replies: 3
Views: 115

Re: georeferencing a voltage

What sort of magnetometer do you have? What are you hoping to detect? Geological features? Hidden magnets? 'Ley lines'? If a mobile phone sensor might work for what you have in mind take a look at this. https://play.google.com/store/apps/details?id=com.chrystianvieyra.android.physicstoolboxmagnetome...
by PiGraham
Wed May 22, 2019 8:26 am
Forum: Beginners
Topic: Need to operate 12 servos at a range of 1200 yards
Replies: 9
Views: 275

Re: Need to operate 12 servos at a range of 1200 yards

jamesh wrote:
Wed May 22, 2019 8:14 am

Shooting range?
That was my thought too.

The OP isn't really a question about RPI, it's about radio comms / remote control.
by PiGraham
Tue May 21, 2019 2:49 pm
Forum: General discussion
Topic: RPI acting both as slave and as master device on its usb ports
Replies: 22
Views: 610

Re: RPI acting both as slave and as master device on its usb ports

So my question is: Hardware wise, how do I have 2 devices connected to a given pi, sharing a network and passing it along a larger chain of pis? Is it possible to have this be "effectively" de-centralized as far as the end user is concerned? Two devices? Is that all you need, one host and two slave...
by PiGraham
Sun May 19, 2019 8:18 pm
Forum: General discussion
Topic: RPI acting both as slave and as master device on its usb ports
Replies: 22
Views: 610

Re: RPI acting both as slave and as master device on its usb ports

This thread touches on mesh WiFi networks on Pi and mentions BATMAN. Could be relevant.

https://www.raspberrypi.org/forums/view ... 3#p1470093
by PiGraham
Sun May 19, 2019 7:44 pm
Forum: General discussion
Topic: RPI acting both as slave and as master device on its usb ports
Replies: 22
Views: 610

Re: RPI acting both as slave and as master device on its usb ports

I suspect you're confusing a hardware level technology (ethernet) with a high level software one (IP aka the internet). Regardless of that, a switch provides no redundancy. You are obviously in a very argumentative mood. Aren't we all trying to help others? The hardware provides multiple redundant ...
by PiGraham
Sun May 19, 2019 12:31 pm
Forum: General discussion
Topic: RPI acting both as slave and as master device on its usb ports
Replies: 22
Views: 610

Re: RPI acting both as slave and as master device on its usb ports

I found you statement " If you connect many RPi slaves to a host RPi through USB hubs the slaves can't talk to each other, only to the host." to be inaccurate (and therefore misleading) as it gave the impression that slaves connected via USB ethernet gadget can communicate only with the host and ne...
by PiGraham
Sun May 19, 2019 11:37 am
Forum: General discussion
Topic: how to connect another USB device when pi zero is turned to HID device?
Replies: 4
Views: 119

Re: how to connect another USB device when pi zero is turned to HID device?

[*]There are such things a spi to USB host chips. While I have no experience of them it may be possible to add a secnd USB port using one of There are. Here's a post containing a suggestion that it works on Rasbian, maybe. https://www.raspberrypi.org/forums/viewtopic.php?t=201262 There are Arduino ...
by PiGraham
Sun May 19, 2019 11:22 am
Forum: General discussion
Topic: setup Raspberry Pi Zero without internet access and only 1 micro usb port
Replies: 14
Views: 339

Re: setup Raspberry Pi Zero without internet access and only 1 micro usb port

You can also access Linux command line via the UART serial port GPIO pins, which you can connect to using a USB serial adaptor and a serial terminal program (e.g. Putty is a good choice on Windows). Make sure the adaptor signals are 3.3Volt level though. I think that by default the serial port is co...
by PiGraham
Sun May 19, 2019 11:13 am
Forum: General discussion
Topic: RPi for button presser
Replies: 19
Views: 446

Re: RPi for button presser

hello guys, New update in this. O have changed my mosfet with logic level mosfet. The circuit got worked. But the solenoid heated up so badly. What should i do to my circuit if want to give 12V external supply? The obvious answer is to use appropriately rated components, so use a 12V solenoid, if y...
by PiGraham
Sun May 19, 2019 10:48 am
Forum: General discussion
Topic: RPI acting both as slave and as master device on its usb ports
Replies: 22
Views: 610

Re: RPI acting both as slave and as master device on its usb ports

Isn't it better to use a switch or router and network the devices? For some values of "better" perhaps. And that wasn't my point, I was clarifying your misleading statement that " the slaves can't talk to each other" You say it's misleading, but your answer is not that slaves can talk to each other...
by PiGraham
Sat May 18, 2019 8:43 pm
Forum: General discussion
Topic: RPI acting both as slave and as master device on its usb ports
Replies: 22
Views: 610

Re: RPI acting both as slave and as master device on its usb ports

A LAN is better suited to a mesh than USB which operates as master/slave. If you connect many RPi slaves to a host RPi through USB hubs the slaves can't talk to each other, only to the host. Not necessarily true. If the slave Pi are zero/zeroW/A/A+ running as ethernet gadgets (or as serial gadgets ...
by PiGraham
Sat May 18, 2019 10:40 am
Forum: General discussion
Topic: RPI acting both as slave and as master device on its usb ports
Replies: 22
Views: 610

Re: RPI acting both as slave and as master device on its usb ports

A LAN is better suited to a mesh than USB which operates as master/slave. If you connect many RPi slaves to a host RPi through USB hubs the slaves can't talk to each other, only to the host.
by PiGraham
Thu May 16, 2019 9:27 pm
Forum: Advanced users
Topic: Raspberry pi socket connection delay for receiving message.
Replies: 3
Views: 126

Re: Raspberry pi socket connection delay for receiving message.

I second the Nagle comment by 6by9. Read up on TCP_NODELAY.
If you want quick responses and your data is n smallish chunks you could use UDP instead of TCP streams.
by PiGraham
Wed May 08, 2019 8:53 pm
Forum: Troubleshooting
Topic: adafruit 16 channel servo driver will not let me make servo go limp
Replies: 9
Views: 172

Re: adafruit 16 channel servo driver will not let me make servo go limp

The servo's I tested are tower pro SG90. Going limp might be over stating it, with power on but the dutycycle set at zero you can turn the output horn but you still need to over come the gearbox and motor resistance. We're as once you set a dutycycle other than zero the servo will resist an attempt...
by PiGraham
Wed May 08, 2019 8:10 pm
Forum: Troubleshooting
Topic: adafruit 16 channel servo driver will not let me make servo go limp
Replies: 9
Views: 172

Re: adafruit 16 channel servo driver will not let me make servo go limp

Just curious. What sort of servos are these that go limp?
How easily do they move?
by PiGraham
Wed May 08, 2019 12:20 pm
Forum: General discussion
Topic: RPi for button presser
Replies: 19
Views: 446

Re: RPi for button presser

You describe the solenoid as "push pull" but only show a single coil and a single sided drive so it can't puseh and pull, can it? Do you mean a spring return solenoid?
by PiGraham
Wed May 08, 2019 12:18 pm
Forum: General discussion
Topic: RPi for button presser
Replies: 19
Views: 446

Re: RPi for button presser

This is the schematic of my RPi where i am using 5V as a Vcc from RPi. You have the diode the wrong way round. You put a diode across a coil reverse polarity to short out the back EMF that is generated when the coil turns off. The way you have shown it the diode will conduct if the FET turns on and...
by PiGraham
Wed May 08, 2019 12:14 pm
Forum: General discussion
Topic: RPi for button presser
Replies: 19
Views: 446

Re: RPi for button presser

Hello Guys, I am making a button presser for that i made a circuit and wrote some code. Its not working. Could you please help me out? I am using 5V push pull Solenoid. I wrote some code but its not happening. What's not happening? What sort of buttons do you hope to push? A lot of solenoids on the...
by PiGraham
Wed May 08, 2019 11:30 am
Forum: Troubleshooting
Topic: adafruit 16 channel servo driver will not let me make servo go limp
Replies: 9
Views: 172

Re: adafruit 16 channel servo driver will not let me make servo go limp

What servos? I don't think most will "go limp" when power is applied.
by PiGraham
Wed May 08, 2019 11:01 am
Forum: Troubleshooting
Topic: False triggering.
Replies: 3
Views: 101

Re: False triggering.

It could be electrical interference. It may help is the wires from sensor to Pi are as short as possible, twisted together and shielded. Cat5 network cable is a handy and cheap source of cable like that. You could try switching electrical devices on and off and see if the camera is triggered at thos...

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