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by Burngate
Sat May 30, 2020 10:51 am
Forum: Automation, sensing and robotics
Topic: Worm Gearbox - External Force Failure Torque
Replies: 7
Views: 569

Re: Worm Gearbox - External Force Failure Torque

Isn't it just a matter of geometry? A worm gear, like a screw thread, is generally at a shallow angle, so a large movement in one direction is needed for a small movement of the gear at right-angles to that, and the forces are inverse to keep the power constant. If the angle were 45° then the moveme...
by Burngate
Sat May 30, 2020 9:11 am
Forum: Beginners
Topic: Read Open Collector output with optocoupler
Replies: 12
Views: 734

Re: Read Open Collector output with optocoupler

Whith the open collector output connected to a gpio input and 50 KO pull-up resistor to 3.3 V of the raspberry pi and fan GND with raspi GND connected the rpm reading is to high. So it could be possible to connect it direcly to your Rpi. I have done that already but with some other devices sensors,...
by Burngate
Fri May 29, 2020 6:03 pm
Forum: Beginners
Topic: Read Open Collector output with optocoupler
Replies: 12
Views: 734

Re: Read Open Collector output with optocoupler

Not sure I understand. Your first link shows a remarkably bad diagram: Systemair.png which isn't quite the same as your last diagram - the pin numbers are different, for a start. The first one implies there's an optoisolator inside the fan, which according to the first post isn't pulling the tach ou...
by Burngate
Fri May 29, 2020 9:30 am
Forum: Beginners
Topic: Limit Switch - "Normally Open" Fail Safe
Replies: 5
Views: 403

Re: Limit Switch - "Normally Open" Fail Safe

If the normally closed wire ceases to be closed AND the normally open wire is not closed, then there is an error and the program should terminate. Depending on the switch, there could be a short period when both NO & NC are unconnected, so if your program detects that, then wait awhile and then che...
by Burngate
Mon May 18, 2020 5:45 pm
Forum: Automation, sensing and robotics
Topic: Current transformers, internal resistance, burden resistors
Replies: 1
Views: 192

Re: Current transformers, internal resistance, burden resistors

You've got a 1000:1 transformer - 1000 turns of wire in the secondary and a single turn in the primary The current in the secondary will be a thousandth of the current in the primary (1mA for every A) and therefore the voltage across the primary will be a thousandth the voltage across the secondary ...
by Burngate
Sun May 10, 2020 8:45 am
Forum: Troubleshooting
Topic: composite out signal distortion
Replies: 9
Views: 492

Re: composite out signal distortion

mad4pi wrote:
Sun May 10, 2020 3:03 am
mahjongg wrote:
Sun May 10, 2020 1:04 am
Sounds like this problem (inverted video signal)
viewtopic.php?p=653422#p653422
I wish the screen output was that good - the distortion is actually a lot worse than that.
Can we see a photo of it?
by Burngate
Sat May 09, 2020 5:57 pm
Forum: Troubleshooting
Topic: Garbled composite output from Pi3b
Replies: 5
Views: 288

Re: Garbled composite output from Pi3b

My take on this: The dark green vertical stripe is the colour burst. The horizontal sync pulse should form a blacker-than-black (less than 0v) vertical stripe to its left. All of that should be in the blanking area, at 0v None of that is there - instead the blanking area is above 0v, so grey compare...
by Burngate
Wed May 06, 2020 9:25 am
Forum: Troubleshooting
Topic: Floating Pins
Replies: 18
Views: 726

Re: Floating Pins

I am never going to agree, detest the use of "ground" and "earth" except when referring to a contact hammered into the planet's soil, so we'll have to agree to disagree. To me "0 volts" or "0 volts rail" is more correct than ground. The first two are the voltage to which other voltages in circuit a...
by Burngate
Mon May 04, 2020 6:14 pm
Forum: General discussion
Topic: Instructions with a new Pi
Replies: 10
Views: 535

Re: Instructions with a new Pi

... a sheet of IKEA style instructions ... IKEA has been producing these things for as long as I've been buying their wardrobes, and for the same length of time I've been knocking on the neighbour's door for clarification. The Chinese invented pictographs long before the Romans invented Latin, and ...
by Burngate
Sat May 02, 2020 6:03 pm
Forum: Beginners
Topic: Help please, R.Pi 3 Model B+ no longer working...
Replies: 11
Views: 458

Re: Help please, R.Pi 3 Model B+ no longer working...

Let him learn - hit him where it hurts - tell him you'll match whatever he can save up, so long as he doesn't do the same again.

How much a week pocket money does he get? At 10, I was getting half-a-crown, so it'd take a fair while to save up for a new one.
And Christmas is coming -he might be lucky.
by Burngate
Fri May 01, 2020 11:05 am
Forum: Automation, sensing and robotics
Topic: Extend IR Led Range
Replies: 16
Views: 1005

Re: Extend IR Led Range

If the forward voltage of the LED is about 1.3v (for ease of calculation) you've allowed 2v across the series resistor, so 10mA through it if the transistor is fully on. But, with 10k feeding the base (so only 0.25mA into it), the transistor is unlikely to be fully on - its hfe drops drastically tow...
by Burngate
Fri May 01, 2020 9:55 am
Forum: Off topic discussion
Topic: Raspberry Pi as a PCIe card concept
Replies: 51
Views: 5667

Re: Raspberry Pi as a card concept

I disagree - he doesn't deserve a ban; he hasn't been rude / derogatory / anything that could get my back up. Admittedly, just like my sainted 93-year-old mother-in-law, I can't quite work out what he's on about half the time, but unlike her, I'm not face-to-face with him, so I don't have to reply. ...
by Burngate
Wed Apr 29, 2020 6:32 pm
Forum: Graphics, sound and multimedia
Topic: Railway Block Instruments using a Raspberry Pi
Replies: 2
Views: 296

Re: Railway Block Instruments using a Raspberry Pi

For those wishing to know more, please email me for further information, photographs and circuit diagrams. This sounds interesting, but my brain isn't up to imagining what's supposed to happen without a diagram. You could upload any photos, circuit diagrams, etc. to a hosting site such as imgur and...
by Burngate
Wed Apr 22, 2020 5:48 pm
Forum: Troubleshooting
Topic: switching fan from 3.3v to 5v makes pi crash
Replies: 7
Views: 433

Re: switching fan from 3.3v to 5v makes pi crash

the 3.3 pin can supply about 500ma earlier models were limited to 50ma so ist fine Not quite true - the 50mA limit applied (and still does) to the total current into / out of GPIOs. If you're happy that the PMIC can supply 500mA on top of everything else it has to supply, and doesn't mind the fan a...
by Burngate
Mon Apr 20, 2020 9:15 am
Forum: General discussion
Topic: will a RJ45 male to USB female adapter work?
Replies: 3
Views: 261

Re: will a RJ45 male to USB female adapter work?

leoj wrote:
Sun Apr 19, 2020 5:01 pm
... im am going to buy a Raspberry Pi model B Rev 2 ...
Best advice - Don't.
That's an old Pi 1B - not Pi 2B.

Perhaps think about a Zero-W and a USB hub?
by Burngate
Sun Apr 19, 2020 9:26 am
Forum: Beginners
Topic: Pi 4 MicroSD card slot loose
Replies: 4
Views: 285

Re: Pi 4 MicroSD card slot loose

... the back two connections ... A close-up picture might help. If you mean what I think you mean, then they're just holding the SD slot in place, so there shouldn't be a problem, at least initially. However, as time passes, stress will be put on the actual connections, so they could fail. They sho...
by Burngate
Sat Apr 18, 2020 5:07 pm
Forum: Beginners
Topic: Why did raspberry pi become a good device for creating a server?
Replies: 16
Views: 847

Re: Why did raspberry pi become a good device for creating a server?

The final word could be changed to any number of things*, and you'd get the same set of answers - because it's a computer.

* not a phaser, or sonic screwdriver.
by Burngate
Sat Apr 18, 2020 9:38 am
Forum: Other projects
Topic: Broadcasting a Composite Video Stream over a Network.
Replies: 4
Views: 329

Re: Broadcasting a Composite Video Stream over a Network.

I think you may be out of luck. The camera is probably the PAL version, since you're in the UK, but in any case its output is analogue. To be able to do anything useful over a network, you need an analogue to digital converter - the trade appears to call it a video decoder, and wants to charge hundr...
by Burngate
Fri Apr 17, 2020 11:06 am
Forum: General discussion
Topic: PWM (gpio 18 ) not outputing 3.3V
Replies: 16
Views: 804

Re: PWM (gpio 18 ) not outputing 3.3V

apKvh3s2.png
apKvh3s2.png (11.63 KiB) Viewed 453 times
Would it be worth while going back a step?
Instead of using PWM at 50kHz try switching the transistor at finger-speed, once a second or so, and see what your meter tells you for each of on and off.
by Burngate
Thu Apr 16, 2020 10:51 am
Forum: Beginners
Topic: Does PWM power supply divide the current drawn of a non-inductive Load along with the divided apply voltage?
Replies: 11
Views: 541

Re: Does PWM power supply divide the current drawn of a non-inductive Load along with the divided apply voltage?

@Burngate, may I know how do I determine what situation/load should I add a capacitor? Some loads like motor they may have inductance and I may not need a capacitor as the current drawn has already been smoothed by the load itself. However, some loads like sensor I must use capacitor to smooth the ...
by Burngate
Wed Apr 15, 2020 6:23 pm
Forum: General discussion
Topic: Hello and some doubts
Replies: 11
Views: 857

Re: Hello and some doubts

Yeah, well, I never said I was perfect.
At least I don't remember saying I was.
Maybe I should learn to read before writing.
by Burngate
Wed Apr 15, 2020 6:20 pm
Forum: Beginners
Topic: Does PWM power supply divide the current drawn of a non-inductive Load along with the divided apply voltage?
Replies: 11
Views: 541

Re: Does PWM power supply divide the current drawn of a non-inductive Load along with the divided apply voltage?

Because I thought PWM frequency is always so high comparing to the inductance of any components in the circuit like wire, air, etc. and so that we can always omit the high and low state of PWM and treat the power supply as its average voltage at anytime. What you're describing is, in essence, a swi...
by Burngate
Wed Apr 15, 2020 6:03 pm
Forum: General discussion
Topic: Hello and some doubts
Replies: 11
Views: 857

Re: Hello and some doubts

Just as an aside ...
Walthary wrote:
Wed Apr 15, 2020 3:46 pm
...i have not found the right place to introduce myself so...
viewtopic.php?f=63&t=224841
by Burngate
Wed Apr 15, 2020 10:33 am
Forum: Beginners
Topic: Does PWM power supply divide the current drawn of a non-inductive Load along with the divided apply voltage?
Replies: 11
Views: 541

Re: Does PWM power supply divide the current drawn of a non-inductive Load along with the divided apply voltage?

Being told the load is non-inductive isn't much help, unfortunately, in part because 0.2A @ 1V applied 2A @ 5V applied Tells us it's very non-linear - not resistive (is it something like an LED?) What it would do with a supply switched by PWM isn't something I could guess at. However, you could perh...
by Burngate
Tue Apr 14, 2020 10:18 am
Forum: General discussion
Topic: Dual microphone noise cancellation
Replies: 15
Views: 753

Re: Dual microphone noise cancellation

Long, long ago, when the World was young, and horses ran round Epsom Downs with crowds cheering them on - remember crowds? Lots of people all together, and no policemen telling them to go home? - microphones (unless they were rifle-mics, to pick the sound of the hooves over the twittering birds) ten...

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