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by PiGraham
Sun Apr 14, 2019 10:18 am
Forum: Beginners
Topic: How to connect a old keyboard to a PI?
Replies: 13
Views: 280

Re: How to connect a old keyboard to a PI?

Yes, USB audio card is the cheap easy option. Then you could run something like Audacity to record the sound.

Here's a sound card billed as specifically a Raspberry Pi compatible device from a Pi reseller but you can get much cheaper ones that will probably work.
by PiGraham
Fri Apr 12, 2019 6:57 pm
Forum: Camera board
Topic: Case for a pinhole camera on the side
Replies: 21
Views: 429

Re: Case for a pinhole camera on the side

Wow, love those cameras. I have a Pi camera V2 with a broken lens, now I know what to do with it :D Hmm 1/100 focal distance = 0.03mm or smaller? Brass shim I have , 0.03mm drill not so much ;) It hadn't occurred to me that you could buy such a minute drill. A pricey item though. https://www.graing...
by PiGraham
Fri Apr 12, 2019 1:44 pm
Forum: Other projects
Topic: Proximity fob based game around the town
Replies: 8
Views: 147

Re: Proximity fob based game around the town

This might be beneficial to the business since it encourages people to visit their premises. "Footfall Frenzy" (TM) ... now there's an idea. Of course one has to have the Pi's with the required bits-n-bobs and if one has 100 locations that's getting close to £5K investment. It would probably be bes...
by PiGraham
Fri Apr 12, 2019 12:02 pm
Forum: Beginners
Topic: Controlling continuous servo motor on Raspberry Pi 3 B+ w/ Python
Replies: 4
Views: 88

Re: Controlling continuous servo motor on Raspberry Pi 3 B+ w/ Python

This servo has positional feedback. https://www.pololu.com/product/3432 A hall effect sensor measures the absolute position and outputs a PWM signal. Read the timing of the PWM to get the position. A typical RC servo PWM signal controls the motor speed and direction. If you have the example code wor...
by PiGraham
Fri Apr 12, 2019 11:40 am
Forum: General discussion
Topic: industrial housing for raspberry
Replies: 4
Views: 169

Re: industrial housing for raspberry

"Industrial" is very open ended. One option is a DIN rail mount case and there are a few of those around. Phoenix contact and Campden boss are two I've seen. Mod my Pi has a nice looking extruded aluminium case https://www.modmypi.com/raspberry-pi/cases-183/raspberry-pi-b-plus2-and-3-cases-1122/pi-b...
by PiGraham
Fri Apr 12, 2019 7:18 am
Forum: Other projects
Topic: Proximity fob based game around the town
Replies: 8
Views: 147

Re: Proximity fob based game around the town

If you go for readers around town you will need to sort out power and mounting sites. Council workers are likely to remove things attached to lampposts without permission, you would technically be damaging property if you screwed things to someone's wall without permission and there is always the ri...
by PiGraham
Fri Apr 12, 2019 7:05 am
Forum: Camera board
Topic: Case for a pinhole camera on the side
Replies: 21
Views: 429

Re: Case for a pinhole camera on the side

I doubt you can get useful images from a Pi camera and a pinhole. A pinhole doesn't let in much light which means you need long exposures with film and a CMOS cameraphone sensor will have too much noise and too short exposure times. Also, the small sixe of pixels on a small sensor will be beyond the...
by PiGraham
Thu Apr 11, 2019 12:59 pm
Forum: Other projects
Topic: Proximity fob based game around the town
Replies: 8
Views: 147

Re: Proximity fob based game around the town

Loving the idea. This would be a good, overlay the real town with fantasy map ? What would the game idea be ? Isn't this basically a classic treasure hunt or geocache game? Or, ah, pokemon go. There are apps that do those. If players have smartphones with GPS you probably don't need tags or hardwar...
by PiGraham
Mon Apr 08, 2019 8:49 am
Forum: Advanced users
Topic: GPIO Expander for my project
Replies: 18
Views: 429

Re: GPIO Expander for my project

Hi i would like some help for a project that i am currently working on. I would like to have 32-40 GPIO pins for my raspberry PI 3 B+ but as you know it doesn't have 40 GPIO pins. I need some information on what expander i can use for my project that will give me 32-40 GPIO pins and that i can easi...
by PiGraham
Sun Apr 07, 2019 1:53 pm
Forum: Advanced users
Topic: GPIO Expander for my project
Replies: 18
Views: 429

Re: GPIO Expander for my project

Hi i would like some help for a project that i am currently working on. I would like to have 32-40 GPIO pins for my raspberry PI 3 B+ but as you know it doesn't have 40 GPIO pins. I need some information on what expander i can use for my project that will give me 32-40 GPIO pins and that i can easi...
by PiGraham
Fri Apr 05, 2019 11:27 am
Forum: Beginners
Topic: USB port to USB port
Replies: 6
Views: 182

Re: USB port to USB port

Possibly you could use an "Easy transfer cable" (mentioned in the other link with USBNET) which is a USB Host bridge chip that provides a fast link between two USB hosts. They were advertised for easy system transfer between Windows PCs but they would probably be useable on Linux. There is an open s...
by PiGraham
Thu Apr 04, 2019 12:28 pm
Forum: RISCOS
Topic: New official keyboard - RISCOS
Replies: 5
Views: 973

Re: New official keyboard - RISCOS

This isn't anything specific to thePi keyboard. You just need to set the numlock default state as you want it. The only difference with this keyboard is that the num pad is not separate but shares keys so you want numlock off by default instead of on. This may help for RISC OS http://www.riscos.com/...
by PiGraham
Thu Apr 04, 2019 12:04 pm
Forum: RISCOS
Topic: New official keyboard - RISCOS
Replies: 5
Views: 973

Re: New official keyboard

Why does the new keyboard fail to give the correct upper case characters (SHIFT) ? I've discovered I can correct this behaviour with (CTRL-SHIFT-NUMLOCK). But why should I have to do this on every boot? Is there some way of getting it to behave normally? I'm mainly using RISC OS by the way. Charles...
by PiGraham
Wed Apr 03, 2019 6:29 am
Forum: Automation, sensing and robotics
Topic: Servo control using PWM
Replies: 6
Views: 287

Re: Servo control using PWM

If you want to save a bit of power or wear on the servo, then you'll need to write your own thing to turn the servo off (send 0 pulses) if it hasn't been used for a while. Your pigpiod suggestion is good. Do you know how most servos behave without a PWM signal? I note that just applying power typic...
by PiGraham
Tue Apr 02, 2019 12:29 pm
Forum: Automation, sensing and robotics
Topic: Servo control using PWM
Replies: 6
Views: 287

Re: Servo control using PWM

Also the reason I need to Start and Stop multiple times, is because I will be using the ServoClass in a flask web app which would run 24x7 so I want to enable the servo only when I want to move it. Check how your servo handles no PWM. It will still draw power and may still move a bit. If you want t...
by PiGraham
Tue Apr 02, 2019 12:26 pm
Forum: Automation, sensing and robotics
Topic: Servo control using PWM
Replies: 6
Views: 287

Re: Servo control using PWM

Maybe this helps: 4 I am fairly sure it is a bug in the RPi.GPIO module. Look through https://sourceforge.net/p/raspberry-gpio-python/tickets/ As a workaround I suggest you do not use the start() and stop() methods in a loop, use the ChangeDutyCycle() method instead to set the duty cycle to zero to ...
by PiGraham
Tue Apr 02, 2019 8:29 am
Forum: Python
Topic: Play tone without generating wave data beforehand
Replies: 7
Views: 153

Re: Play tone without generating wave data beforehand

You could use pygame.midi and a soft synth like timidity (included in Rasbian)
by PiGraham
Sat Mar 30, 2019 3:58 pm
Forum: Beginners
Topic: Optical Quadrature Rotary Encoder
Replies: 2
Views: 74

Re: Optical Quadrature Rotary Encoder

The data sheet says the outputs are "Open collector and NPN configuration" so you shouldn't need a level shifter. The outputs will pull Pi inputs down to 0V when they switch and the Pi pullups will give a safe high level otherwise.
by PiGraham
Fri Mar 29, 2019 9:55 pm
Forum: General discussion
Topic: How long will it stay on with a external battery?
Replies: 33
Views: 725

Re: How long will it stay on with a external battery?

Calculation(s) are good for reference only Real-world values, made/acquired during actual testing/use is much preferred Accurate calculations are far more useful than individual anecdotes. Unless someone else is using the exact same parts and running the exact same tasks their run time can't be rel...
by PiGraham
Fri Mar 29, 2019 11:01 am
Forum: General discussion
Topic: How long will it stay on with a external battery?
Replies: 33
Views: 725

Re: How long will it stay on with a external battery?

Having been directly criticized twice for my reply, can point out again that the OP only provided two "facts' as a the basis for their question: i have a raspberry pi 3 b+ and i have a 20100 mah external battery I tried to indicate, perhaps too gently, that a reliable reply could not be provided fr...
by PiGraham
Fri Mar 29, 2019 10:26 am
Forum: General discussion
Topic: How long will it stay on with a external battery?
Replies: 33
Views: 725

Re: How long will it stay on with a external battery?

MOst power packs aren't going to warn the Pi before they shut off at minimum charge level. This could cause problems with SD corruption. To ensure clean shutdown you could use a UPS that signals before shutdown, you could use an ADC to measure battery cell voltage (not the regulated output voltage) ...
by PiGraham
Fri Mar 29, 2019 10:16 am
Forum: General discussion
Topic: How long will it stay on with a external battery?
Replies: 33
Views: 725

Re: How long will it stay on with a external battery?

Hello, i have a raspberry pi 3 b+ and i have a 20100 mah external battery. How long can i keep the raspberry pi on? A trivial calculation is very simple, so hardly worth a question in a forum - From: https://www.raspberrypi.org/documentation/faqs/#pi-power Raspberry Pi 3 Model B+ Typical bare-board...
by PiGraham
Tue Mar 26, 2019 6:29 pm
Forum: Troubleshooting
Topic: [SOLVED] Can't get my servos to go where they're supposed to go?
Replies: 19
Views: 340

Re: Can't get my servos to go where they're supposed to go?

Just destroying the end stops does not create a continuous rotation servo. The internal feedback electronics also have to be replaced. Do they change speed? If the feedback pot is damaged it doesn't make a proper continuous rotation servo, but it could result in continuous rotation. Just commanding...
by PiGraham
Tue Mar 26, 2019 4:35 pm
Forum: Troubleshooting
Topic: [SOLVED] Can't get my servos to go where they're supposed to go?
Replies: 19
Views: 340

Re: Can't get my servos to go where they're supposed to go?

raspberrystrawberry wrote:
Tue Mar 26, 2019 4:07 pm

edit: I think the servos are busted.. or they're secretly continuous ..
That seems possible. A servo relies on potentiometer (pot) turned by the output shaft to measure the position. If that pot doesn't turn with the shaft the motor will keep turning.
by PiGraham
Tue Mar 26, 2019 10:26 am
Forum: General discussion
Topic: RPI acting both as slave and as master device on its usb ports
Replies: 4
Views: 131

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

I agree with Hippy, you can't use the one USB on the SOC as both host and device at the same time. The four USB ports on Pi are a USB hub attached to the single USB host port, so you can't use OTG gadget mode on a Pi with four USB sockets. You can run in gadget mode so the Pi looks like a keyboard a...

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