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by pcmanbob
Tue Jun 18, 2019 8:40 pm
Forum: Automation, sensing and robotics
Topic: how to control 24VDC valve with ULN2803A?
Replies: 23
Views: 1941

Re: how to control 24VDC valve with ULN2803A?

I don't see what you think you need the resistor for. The pi gpio drives the input pins on the chip directly, and the output pins on the chip provide the ground to what ever device you are trying to control. In the diagram I posted on this thread there are no resistors what so ever. Edit. Looking at...
by pcmanbob
Tue Jun 18, 2019 8:28 pm
Forum: Beginners
Topic: 3v3 Relay with external power supply
Replies: 13
Views: 200

Re: 3v3 Relay with external power supply

Even though the seller claims it will work with the pi 3.3v gpio he provides not detail as to how to connect it or if it's active high or active low. If you really want to be sure you relay will work with the pi why not just build your own driver circuit to control which ever relay you want. For a s...
by pcmanbob
Tue Jun 18, 2019 5:28 pm
Forum: Beginners
Topic: 3v3 Relay with external power supply
Replies: 13
Views: 200

Re: 3v3 Relay with external power supply

Can't say if you selected relay will work as the link just takes me to a sign in page.

Even if we could see the relay you want to use we may still not know unless some one here has actually tried that exact device.
by pcmanbob
Tue Jun 18, 2019 9:00 am
Forum: Automation, sensing and robotics
Topic: Limit Switch
Replies: 4
Views: 116

Re: Limit Switch

This is an example of using a switch to stop a motor when the switch state changes. import RPi.GPIO as gpio import time gpio.setmode(gpio.BCM) gpio.setup(17, gpio.OUT) gpio.setup(22, gpio.OUT) gpio.setup(21, gpio.IN, pull_up_down=GPIO.PUD_UP) seconds = 10 print "reverse" gpio.output(17, False) gpio....
by pcmanbob
Mon Jun 17, 2019 6:39 pm
Forum: Troubleshooting
Topic: RPi 3 and TB6600 cannot control bipolar stepper motor
Replies: 2
Views: 66

Re: RPi 3 and TB6600 cannot control bipolar stepper motor

These controllers required a 5v control pulse , but the pi only has a 3.3v gpio , connecting the (PUL+ DIR+ ENA+) to 5v and trying to use gpio to control it will result in damage to your pi, because the gpio is not 5v tolerant ( any input over 4v will damage gpio/pi ) you need to use a transistor in...
by pcmanbob
Mon Jun 17, 2019 2:17 pm
Forum: Other projects
Topic: ADS1115 is not detected by i2c
Replies: 5
Views: 131

Re: ADS1115 is not detected by i2c

With problems involving connection issues its away a good idea to post some pictures showing the wiring and both the pi and device ends so we can check you actually have it connected correctly, its surprising how may times a simple wiring error is the cause of the problem. just upload you images to ...
by pcmanbob
Mon Jun 17, 2019 2:03 pm
Forum: Automation, sensing and robotics
Topic: DS18B20 resolution
Replies: 14
Views: 422

Re: DS18B20 resolution

Accuracy of the DS18B20 is 0.5 Celsius. Half of a full degree!!! It is normal to get more resolution than accuracy otherwise you couldn't get a good accuracy! At 12 bits you are at 0.0625 Celsius which is a little more than 1 decimal resolution. So why are you looking at 3 decimals when the resolut...
by pcmanbob
Mon Jun 17, 2019 1:55 pm
Forum: Off topic discussion
Topic: [FIXED] Ego Search / Own Posts failing
Replies: 54
Views: 4757

Re: [FIXED] Ego Search / Own Posts failing

Thanks jamesh for the update

I guess I am not the only one hampered by this..
by pcmanbob
Mon Jun 17, 2019 12:31 pm
Forum: General discussion
Topic: Generate multiple PWM signals
Replies: 5
Views: 161

Re: Generate multiple PWM signals

Hi.

Actually the pi can generate several software PWM signals which should all you need for speed control on an L298D

if you want to drive things like servos then look at joan's pigpio library, which of course you could also use to provide PWM signals to your L298D

http://abyz.me.uk/rpi/pigpio/
by pcmanbob
Mon Jun 17, 2019 12:23 pm
Forum: Off topic discussion
Topic: [FIXED] Ego Search / Own Posts failing
Replies: 54
Views: 4757

Re: [FIXED] Ego Search / Own Posts failing

So its been nearly a month since the update to the forum that broke the ego search, while most of the problems seem to have been solved we are having to wait till the next day for the first post on a thread to show up in the ego search. while this might not seem like much of a problem when you reply...
by pcmanbob
Mon Jun 17, 2019 10:14 am
Forum: Python
Topic: Function going through twice
Replies: 17
Views: 465

Re: Function going through twice

Well if you disabled the event and still had the file writes in place and then re enabled the event after the file writes , it has to ether be a button press or something causing your pi to think there has been a button press , as you still have not posted your complete program or a digram of how yo...
by pcmanbob
Mon Jun 17, 2019 9:52 am
Forum: Beginners
Topic: controlling traffic light with PI
Replies: 2
Views: 104

Re: controlling traffic light with PI

You have already asked this question and had a reply here https://www.raspberrypi.org/forums/viewtopic.php?f=48&t=242893 please don't double post. just in case the wrong thread gets deleted reposting answer here. As a starting point why not take a look at the physical computing lessons on the raspbe...
by pcmanbob
Mon Jun 17, 2019 9:47 am
Forum: Staffroom, classroom and projects
Topic: art project with a traffic light
Replies: 4
Views: 201

Re: art project with a traffic light

As a starting point why not take a look at the physical computing lessons on the raspberry pi site it includes making traffic lights using LED's as one of the lessons. https://projects.raspberrypi.org/en/projects/physical-computing/11 then I suggest you do some searching on the web you will find lot...
by pcmanbob
Mon Jun 17, 2019 9:43 am
Forum: Troubleshooting
Topic: Servo motor only turns one way on video streaming server
Replies: 1
Views: 40

Re: Servo motor only turns one way on video streaming server

Hi.

You should not use p.stop() there is a bug in the RPI.GPIO code that causes the pwm to stop working until the pi is rebooted once p.stop() has been called. if you want to stop the servo gittering just set the duty cycle to 0
by pcmanbob
Mon Jun 17, 2019 9:33 am
Forum: Python
Topic: Function going through twice
Replies: 17
Views: 465

Re: Function going through twice

If its not switch bounce , have you check your wiring for a bad connection ?

I cant see it being interference or induced voltages at your function would be running randomly, could it be your power supply being loaded and dropping its voltage ?
by pcmanbob
Mon Jun 17, 2019 9:27 am
Forum: Automation, sensing and robotics
Topic: DS18B20 resolution
Replies: 14
Views: 422

Re: DS18B20 resolution

Following the failure of my waterproof sensors I decided to strip them down and replace the DS18B20 with some I have from a better supplier, once thing I did notice on stripping down the second on is that the soldered connections looked greenie/brown and broke away very easily so may be that was the...
by pcmanbob
Sun Jun 16, 2019 7:49 pm
Forum: Python
Topic: Function going through twice
Replies: 17
Views: 465

Re: Funtion going through twice

So we have finally proved it's an actual second input on the gpio causing the function to run twice. So your a step closer to solving the problem or you could just leave the function as it is so it stops the calling of the function while it's running. I would guess it's switch bounce causing the sec...
by pcmanbob
Sun Jun 16, 2019 6:00 pm
Forum: Troubleshooting
Topic: Espeak alsa issue
Replies: 5
Views: 138

Re: Espeak alsa issue

Well it used to work, I last tested it and had it working in feb 2018 on stretch, viewtopic.php?t=206190

So I guess there has been an update at some point after that, which results in espeak no longer working on stretch.
by pcmanbob
Sun Jun 16, 2019 5:04 pm
Forum: General discussion
Topic: Supplying 5v power to RPi & 120VAC to relays
Replies: 14
Views: 324

Re: Supplying 5v power to RPi & 120VAC to relays

What you are talking about producing is a prototype, they are often assembled from components like the ones I linked to , once things are more finalised with the design then you start building custom PCBs to intergrate your design in to one or two PCBs for your final design. The raspberry pi power s...
by pcmanbob
Sun Jun 16, 2019 4:13 pm
Forum: General discussion
Topic: Supplying 5v power to RPi & 120VAC to relays
Replies: 14
Views: 324

Re: Supplying 5v power to RPi & 120VAC to relays

@pcmanbob my question isn't as much about design as it is where to find the needed components. I've searched mouser.com and wasn't able to come up with anything that fit what I'm looking for. This seemed like a common enough situation that someone would sell an off the shelf solution but maybe that...
by pcmanbob
Sun Jun 16, 2019 4:02 pm
Forum: Other projects
Topic: Wire GPIO into remote control PCB?
Replies: 7
Views: 198

Re: Wire GPIO into remote control PCB?

Well without knowing more about the remote its hard to say, but in general you could use a relay driven by the gpio , with its contact wired across the switch so when activated by the pi it makes the same connection as pressing the switch would . you may be able to do the same thing using an opto is...
by pcmanbob
Sun Jun 16, 2019 3:53 pm
Forum: General discussion
Topic: Supplying 5v power to RPi & 120VAC to relays
Replies: 14
Views: 324

Re: Supplying 5v power to RPi & 120VAC to relays

If you are coming to a forum that's pi computer based and asking electrical design questions I would say you seriously need to take a step back and think about what you are doing, you obviously have no electrical qualifications. mains voltage will kill you and burn down your house given the chance. ...
by pcmanbob
Sun Jun 16, 2019 3:14 pm
Forum: Troubleshooting
Topic: Espeak alsa issue
Replies: 5
Views: 138

Re: Espeak alsa issue

Hi. If you want help its no good just writing "expression : blah blah has been failed at blah blah" we need the exactly error message posted here so we can see what's failing on your pi. may be you should try following the tutorial here to get espeak working. https://www.dexterindustries.com/howto/m...
by pcmanbob
Sun Jun 16, 2019 3:06 pm
Forum: Off topic discussion
Topic: how heavy is raspbian ?
Replies: 30
Views: 907

Re: how heavy is raspbian ?

Well if you are talking about weight the layer of dust that will eventually form on your pi will have more affect upon its weight that the software loaded on it and we are probably not even talking about a layer of dust your could see.

:lol: :lol:
by pcmanbob
Sun Jun 16, 2019 2:54 pm
Forum: Python
Topic: servo control
Replies: 10
Views: 255

Re: servo control

Edit. opps missed the end of your post comes from viewing on a tablet while doing other things. Edit2. so back on my pc running your code on a pi reveals the problem. BUTTON1=16 # >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> set variable here to 16 BUTTON2=18 GPIO.setup(BUTTON1,GPIO.IN,pu...

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