Go to advanced search

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: 366

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: 636

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: 636

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...
by PiGraham
Thu Apr 05, 2018 6:37 pm
Forum: Other projects
Topic: TCS34725 RGB sensor
Replies: 4
Views: 236

Re: TCS34725 RGB sensor

Is it the range value of the red, green and blue color will be changing if the distance is different? The RGB sensor doesn't know anything about range (distance), only how many photons of light hit it's different zones. If the distance between light source and sensor varies the number of photon wil...
by PiGraham
Thu Apr 05, 2018 9:27 am
Forum: Other projects
Topic: TCS34725 RGB sensor
Replies: 4
Views: 236

Re: TCS34725 RGB sensor

Yellow is roughly equal levels of red and green. So when you measure red the RGB sensor might read some values where the red value is much larger than G or B. Just making up some values as an example let's say: - Red light R = 90, G=15, B=9 Green light R = 21, G=106, B=12 So maybe...0 Yellow light R...
by PiGraham
Wed Apr 04, 2018 3:12 pm
Forum: Python
Topic: Detection of the traffic light status (Detecting Traffic Light Colour)
Replies: 22
Views: 636

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

I'm asume this is a proof of concept thing to do That's a fair point. If a red and green ( and possibly amber ) LED is placed in a sealed tube at one end with the RGB sensor at the other it should be possible to show that different sounds can be produced for each LED lit. Actually putting it in the...
by PiGraham
Wed Apr 04, 2018 1:16 pm
Forum: Python
Topic: Detection of the traffic light status (Detecting Traffic Light Colour)
Replies: 22
Views: 636

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

Absolutely but, I'm asume this is a proof of concept thing to do, I have no idea what age Final Year is w.r.t age. I am assuming GCSE (16yr) or A-Level (18yr) if in the UK or similar course. Detect a colour, give it a tolerance as not all reds are the same, then have it play a sound. See if they ca...
by PiGraham
Wed Apr 04, 2018 11:22 am
Forum: Automation, sensing and robotics
Topic: Temperature sensor for monitoring temperature of aluminum plate
Replies: 5
Views: 234

Re: Temperature sensor for monitoring temperature of aluminum plate

3D printers do this using bead thermistors
Heating with a resistor seems likely to be quite uneven. 3D printers use PCB heaters or mats with zig-zags of heating wire.
by PiGraham
Wed Apr 04, 2018 10:44 am
Forum: Python
Topic: Detection of the traffic light status (Detecting Traffic Light Colour)
Replies: 22
Views: 636

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. The pedestrian signals are a green light and a red li...
by PiGraham
Wed Apr 04, 2018 8:57 am
Forum: Python
Topic: Detection of the traffic light status (Detecting Traffic Light Colour)
Replies: 22
Views: 636

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

Do you know about this feature of UK PELICAN crossings? https://www.youtube.com/watch?v=fRPWlBAgSnw The idea to make an aid for the visually impaired is a good one but I don't think an RGB sensor on a stick is a safe way to sense the state of a crossing. The sensor would have to be on a telescope to...
by PiGraham
Tue Apr 03, 2018 8:58 pm
Forum: Beginners
Topic: NFC lockers
Replies: 10
Views: 248

Re: NFC lockers

If you need to make your own lock mechanisms you could try using car central locking actuators. They would be fairly straightforward to interface, just as 12V dc motors on an h-bridge (but take a few amps)
and just give you push pull motion with quite a bit of force.
Cheap too.
by PiGraham
Tue Apr 03, 2018 8:39 pm
Forum: Beginners
Topic: NFC lockers
Replies: 10
Views: 248

Re: NFC lockers

A furthe though occurs: not every phone is NFC capable, and not everyone will want to take their phone into the gym with them. That one is easily deatl with. NFC cards, tags and stickers are reasily available and cheap. Include NFC in a membership card and also allow a phone to be enrolled into the...
by PiGraham
Tue Apr 03, 2018 8:27 pm
Forum: Beginners
Topic: How would I set up Rasperry Pi for sensing doorbell push..?
Replies: 8
Views: 286

Re: How would I set up Rasperry Pi for sensing doorbell push..?

Some info on reading wireless doorbell codes. Looks promising. https://www.rtl-sdr.com/wireless-door-bell-433-mhz-ask-signal-analysis-with-a-hackrf/ https://www.amazon.co.uk/interface-Raspberry-Doorbells-Compatible-electronics/dp/B00T4DUYMS http://www.securipi.co.uk/remote-433-receivers.pdf https://...
by PiGraham
Tue Apr 03, 2018 6:40 pm
Forum: Beginners
Topic: Proper way of extending cable range of water sensor LM393?
Replies: 27
Views: 942

Re: Proper way of extending cable range of water sensor LM393?

http://www.fondriest.com/environmental-measurements/wp-content/uploads/2014/02/conductivity_averages-300x265.jpg http://www.fondriest.com/environmental-measurements/parameters/water-quality/conductivity-salinity-tds/#cond5 Just be aware that conductivity of water can vary over at least 50,000:1 ran...
by PiGraham
Tue Apr 03, 2018 4:14 pm
Forum: Beginners
Topic: Proper way of extending cable range of water sensor LM393?
Replies: 27
Views: 942

Re: Proper way of extending cable range of water sensor LM393?

The sensors I got, work by sending a signal if there is electricity flowing between two sensor spades/probes. It is resistive principle? So I guess that is a very good mechanism for water leak detection. What is the water you hope to etect? If it's seawater you'll be OK, but pure water is an insula...
by PiGraham
Tue Apr 03, 2018 3:36 pm
Forum: Other projects
Topic: Connecting 50 Solenoids to a Single Pi
Replies: 17
Views: 600

Re: Connecting 50 Solenoids to a Single Pi

mahjongg wrote:
Tue Apr 03, 2018 3:21 pm
Per crosspoint in the matrix the LED/solenoid/reed-relay (whatever) can only draw the maximum current a GPIO pin can deliver, that is 16mA
I suggested driving rows and columns with H-Bridges since that allows polarity reversal for push and pull operation.
by PiGraham
Tue Apr 03, 2018 3:28 pm
Forum: Beginners
Topic: How would I set up Rasperry Pi for sensing doorbell push..?
Replies: 8
Views: 286

Re: How would I set up Rasperry Pi for sensing doorbell push..?

Anyway to just use something that is purely wireless? Like an always listening 433mhz rf receiver module? When doorbell button is pushed, it listens and does what I want it do? Well unless you can figure out what code sequence your individual doorpush transmits and are smart enough to write code to...
by PiGraham
Tue Apr 03, 2018 2:34 pm
Forum: Python
Topic: Detection of the traffic light status (Detecting Traffic Light Colour)
Replies: 22
Views: 636

Re: Guide for Python in Raspberry Pi

So far, I am using TCS34725 RGB Sensor to detect the color of the traffic light. I think you need to describe your concept here. Where is the bit that you want to make a noice relative to the three lights on the tarffic light? Is this the usual roadside traffic light with three lamps, mounted on a ...
by PiGraham
Tue Apr 03, 2018 2:26 pm
Forum: Beginners
Topic: Does osmc support 3.5inch display panel on raspberry pi
Replies: 3
Views: 115

Re: Does osmc support 3.5inch display panel on raspberry pi

Hi everyone its my first post on this forum. Let me be clear cut to my query, so i have a raspberry pi 3 model b and i want to run osmc on it by connecting a 3.5 inch touch display to it so guys please tell me weather it is possible to use osmc on 3.5 inch display and if yes then what steps should ...
by PiGraham
Tue Apr 03, 2018 2:16 pm
Forum: Beginners
Topic: NFC lockers
Replies: 10
Views: 248

Re: NFC lockers

Get a spare locker to experiment on so you can work out all the details without messing up your working lockers.
by PiGraham
Tue Apr 03, 2018 2:14 pm
Forum: Beginners
Topic: NFC lockers
Replies: 10
Views: 248

Re: NFC lockers

Are you a beginner in all aspects o his task or do you have some expertise in some of it? It seems like a tall order to do something like this starting from scratch. You really could end up making a mess of your lockers. At minimum I would you say you need professionally designed locking mechanism t...
by PiGraham
Tue Apr 03, 2018 1:48 pm
Forum: Beginners
Topic: Raspberrypi as small personal computer ?
Replies: 9
Views: 438

Re: Raspberrypi as small personal computer ?

You can also use POE injector/splitter modules to get a 5V supply for the Pi without using a HAT.
by PiGraham
Tue Apr 03, 2018 7:45 am
Forum: Beginners
Topic: Proper way of extending cable range of water sensor LM393?
Replies: 27
Views: 942

Re: Proper way of extending cable range of water sensor LM393?

I am already using a pi with Mqtt. But I need the sensors as waterdetection leak sensor. So they must be working and checking the whole time. Do soil moistiure sensors of the type you posted work as leak detectors? Liqyuid water is going to behave differently to moist soil. As for "checking the whi...
by PiGraham
Mon Apr 02, 2018 5:17 pm
Forum: Beginners
Topic: Proper way of extending cable range of water sensor LM393?
Replies: 27
Views: 942

Re: Proper way of extending cable range of water sensor LM393?

You could look into using battery powered Wi-Fi enabled probes based on ESP8266 modules that are very cheap and can run for many months on two AA batteries. That gest rid of the wires. Use a Pi as a MQTT server to receive occasional updates from all the sensors. SOme useful pointers here https://git...

Go to advanced search