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by PiGraham
Thu Apr 19, 2018 12:48 pm
Forum: Automation, sensing and robotics
Topic: What Optical Sensors for Archery?
Replies: 2
Views: 18

Re: What Optical Sensors for Archery?

That sounds challenging. My initial thoughts are: 1. Use a Pi camera to look across the face of the board at a difuse light on the other side and mount these on a rotating arm so that you can get multiple views of the arrows from all sides. This could involve some tricky maths. It has a lot in commo...
by PiGraham
Thu Apr 19, 2018 11:14 am
Forum: Automation, sensing and robotics
Topic: Finding a sensor to log shock travel on a vehicle
Replies: 4
Views: 83

Re: Finding a sensor to log shock travel on a vehicle

You want to measure how far car shock absorbers move? Sombeody posted on this forum a few days ago mentioning a type of sensor I hadn't heard of before. I can't find that post, but one name for these sensors is "cable extension transducer". Some expensive looking examples are here https://www.varioh...
by PiGraham
Thu Apr 19, 2018 10:40 am
Forum: Raspbian
Topic: Pi 3B+ 2.4ghz works but not 5ghz wifi
Replies: 2
Views: 73

Re: Pi 3B+ 2.4ghz works but not 5ghz wifi

You could check that the channel rou router is using is within the range your Pi is open to. I think that is controlled by region codes on both devices but check the channel number. If you can connect to the router from a Windows PC you can see the channel in use on the properties of the network. I ...
by PiGraham
Thu Apr 19, 2018 7:34 am
Forum: Advanced users
Topic: Syncing a high power LED array to camera start frame.
Replies: 30
Views: 626

Re: Syncing a high power LED array to camera start frame.

You have a strange attitude. If you did want to use a DSLR take a look at gphoto2 which should allow you to download images as they are taken using USB. Since the issues discussed relate to the sensor changing to another SBC will make no difference. And to reiterate, you can use rolling shutter sens...
by PiGraham
Wed Apr 18, 2018 2:26 pm
Forum: Troubleshooting
Topic: add delay raspivid
Replies: 10
Views: 183

Re: add delay raspivid

Could a fifo buffer be used to queue 10 seconds of video through stdout? Hmm, that might work as well, although not sure how you would introduce a delay, apart from maybe starting the receiving end of FIFO later. It was just a thought. I suppose that if the proper frame rate is defined, rather that...
by PiGraham
Wed Apr 18, 2018 1:21 pm
Forum: Troubleshooting
Topic: add delay raspivid
Replies: 10
Views: 183

Re: add delay raspivid

Could a fifo buffer be used to queue 10 seconds of video through stdout?
by PiGraham
Wed Apr 18, 2018 9:33 am
Forum: Advanced users
Topic: Help building a greenhouse system
Replies: 6
Views: 121

Re: Help building a greenhouse system

Run some LED lights Do you need the solar panel to power everything including watering system and lights? Are those "grow lights"? How much energy will be needed to run the system? If you can rely on, say, 5W average over 24 hours you might not have enough for low level task lighting and definitely...
by PiGraham
Wed Apr 18, 2018 8:59 am
Forum: Advanced users
Topic: Help building a greenhouse system
Replies: 6
Views: 121

Re: Help building a greenhouse system

I need help building a greenhouse system that will monitor, record, automate and control the greenhouse. 12V 110AH Deep Cycle Leisure Battery 25W Solar Panel ... Run some LED lights Do you need the solar panel to power everything including watering system and lights? Are those "grow lights"? How mu...
by PiGraham
Mon Apr 16, 2018 8:43 pm
Forum: General discussion
Topic: Anyone using a 4 digit 7 segment display to scroll IP address?
Replies: 3
Views: 109

Re: Anyone using a 4 digit 7 segment display to scroll IP address?

How are the 7 segment displays connected? Do you have documentation or example code? Scrolling an IP address should be simple enough once you know how to put a digit on the display. I see SCLK, DIO & RCLK. At a guess you clock segments states in from DIO on one cock and address the digits in turn wi...
by PiGraham
Mon Apr 16, 2018 4:13 pm
Forum: Advanced users
Topic: Syncing a high power LED array to camera start frame.
Replies: 30
Views: 626

Re: Syncing a high power LED array to camera start frame.

The maximum speed of what I want to take images of is 15m/sec with an exposure time of 1.5ms that means the object will only have moved 2cm during the exposure time. And objects are traveling towards the camera so it wont be an issue. Frame rate is more significant than exposure time. The fastest I...
by PiGraham
Mon Apr 16, 2018 10:50 am
Forum: Automation, sensing and robotics
Topic: how to control multiple valves with single GPIO pin?
Replies: 9
Views: 298

Re: how to control multiple valves with single GPIO pin?

It looks like you can communicate with those Digispark boards over USB, so if you have a couple of USB ports free that would give you 8 extra IO pins without using any of the RPi pins. You can do that, but then you need USB hubs to split out to lots of boards. I was thinking of using a shared seria...
by PiGraham
Mon Apr 16, 2018 7:44 am
Forum: Advanced users
Topic: Syncing a high power LED array to camera start frame.
Replies: 30
Views: 626

Re: Syncing a high power LED array to camera start frame.

Are you trying to freeze motion? It doesn't look like anything is moving in the image from the Pi camera with LED lighting. Here is one of my freeze motion shots, taken from the shore. Great photos. I was asking about whether you were using strobbed LEDs to freeze motion, which is where rolling shu...
by PiGraham
Mon Apr 16, 2018 7:40 am
Forum: Advanced users
Topic: Syncing a high power LED array to camera start frame.
Replies: 30
Views: 626

Re: Syncing a high power LED array to camera start frame.

Also you can get a zillion different hi-quality camera lens on gumtree or craigslist for less than $100 while hi quality CCTV lens are expensive and because of their size don't let in enough light. You want to try and get lens that are NOT full format, if you do use one then your picture will be zo...
by PiGraham
Mon Apr 16, 2018 7:24 am
Forum: Automation, sensing and robotics
Topic: how to control multiple valves with single GPIO pin?
Replies: 9
Views: 298

Re: how to control multiple valves with single GPIO pin?

YOu can run DMX on ATTiny Arduinos.
http://forum.arduino.cc/index.php?topic=264850.0

You can get ATTiny boards such as DIgistump for less than £2
https://www.banggood.com/Digispark-Kick ... 53375.html

They have 6 gpios each
by PiGraham
Sun Apr 15, 2018 8:36 pm
Forum: Advanced users
Topic: Syncing a high power LED array to camera start frame.
Replies: 30
Views: 626

Re: Syncing a high power LED array to camera start frame.

ooops I nearly forgot with a rolling shutter it's not really exposure time but the amount of gain of the CCD chip, silly me. It really is exposure time. It's just that each line of the image exposes at a different time,, one after the other, but each line exposes (gathers light) for the specified e...
by PiGraham
Sun Apr 15, 2018 4:09 pm
Forum: Advanced users
Topic: Syncing a high power LED array to camera start frame.
Replies: 30
Views: 626

Re: Syncing a high power LED array to camera start frame.

Thanks for posting those images. It's great to see what people are doing with Raspberry Pis. It looks very impressive.
Are you trying to freeze motion? It doesn't look like anything is moving in the image from the Pi camera with LED lighting.
by PiGraham
Sun Apr 15, 2018 2:27 pm
Forum: Automation, sensing and robotics
Topic: Long-Range RPI communication with mobile device
Replies: 16
Views: 491

Re: Long-Range RPI communication with mobile device

Think there is a bit of an issue here. Sending 1MB of data and trying to get a response within 0.1 to 1 second, I think is a tall order. Even 1Mb. By response, I mean time taken to start sending the waypoint information until you want the drone to change course. Less that 1MB per file approx 800kb....
by PiGraham
Sat Apr 14, 2018 6:07 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Need to control 48 solenoids from Raspberry Pi
Replies: 2
Views: 87

Re: Need to control 48 solenoids from Raspberry Pi

This is basically the same question posed here https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=210693 https://www.raspberrypi.org/forums/viewtopic.php?f=41&t=209663 You can choose to add lots of gpio expanders on the Pi and run lots of wires to lots of transistors or you could wire a serial ...
by PiGraham
Sat Apr 14, 2018 8:48 am
Forum: Advanced users
Topic: Syncing a high power LED array to camera start frame.
Replies: 30
Views: 626

Re: Syncing a high power LED array to camera start frame.

As 6by9 explained (read the linked info) you can't use strobbed illumination with the rolling shutter at shutter times shorter than the full frame time. If you try you will only illuminate some strip of lines. The scan lines expose at different times. This is nothing like a film camera or gloabl sh...
by PiGraham
Fri Apr 13, 2018 2:36 pm
Forum: Advanced users
Topic: Syncing a high power LED array to camera start frame.
Replies: 30
Views: 626

Re: Syncing a high power LED array to camera start frame.

Yes it seems to work better just using the Camera LED signal to switch the FET directly on and off. When you do as I have done you get a small band at the top of the picture which is the delay in switching on the FET using my python code. I will put a scope on it tomorrow and see what the differenc...
by PiGraham
Wed Apr 11, 2018 1:51 pm
Forum: Automation, sensing and robotics
Topic: how to control multiple valves with single GPIO pin?
Replies: 9
Views: 298

Re: how to control multiple valves with single GPIO pin?

Use some sort of serial bus. i2c, SPI, 1-Wire,rs422,CAN,UART Use the bus to talk to slave device(s) that do the individual switching. If there is some distance between the Pi and the valves it might be best to cover most of the distance with the serial bus and use a bus with robust signalling such a...
by PiGraham
Fri Apr 06, 2018 11:36 am
Forum: Python
Topic: Detection of the traffic light status (Detecting Traffic Light Colour)
Replies: 22
Views: 556

Re: Detection of the traffic light status (Detecting Traffic Light Colour)

On lack of standardisation and the rotating cone: Do all crossings have cones? No. Crossings are maintained by local authorities which are not legally obliged to make them accessible. The Department for Transport says it encourages their use, though, and says that all signal-controlled crossings can...
by PiGraham
Fri Apr 06, 2018 8:49 am
Forum: Python
Topic: Detection of the traffic light status (Detecting Traffic Light Colour)
Replies: 22
Views: 556

Re: Detection of the traffic light status (Detecting Traffic Light Colour)

That sensor will work if they can place it directly in front of the light . But which light? The button box lights up an off-white "WAIT" which goes out when it's safe to cross. Easy to reach but it's easier and safer to use the rotating button. Not in my part of Hampshire they don't. The "press fo...

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