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by davidcoton
Fri Sep 21, 2018 3:44 pm
Forum: Beginners
Topic: Guide on powering Raspberry Pi 3 B+ with ATX PSU?
Replies: 7
Views: 137

Re: Guide on powering Raspberry Pi 3 B+ with ATX PSU?

Or have a look at this (Disclaimer: not tested by me.)
by davidcoton
Fri Sep 21, 2018 3:26 pm
Forum: Beginners
Topic: GPIO Pin Audio Speaker, how?
Replies: 9
Views: 612

Re: GPIO Pin Audio Speaker, how?

mahjongg wrote:
Fri Sep 21, 2018 1:56 pm
the solution described here
Where, exactly? :oops: :roll: :? :o :shock: :lol:
by davidcoton
Thu Sep 20, 2018 10:35 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: how to use the GPIOs
Replies: 14
Views: 341

Re: Hardware

I am qualified both as an electrician and as a programmer. I am qualified as a programmer, electronics and electrical engineer, and as an electrician. I have earnt my living in each of those fields at different times. I still find it daunting to interpret component specifications correctly and desi...
by davidcoton
Sat Sep 15, 2018 9:55 pm
Forum: Advanced users
Topic: Is the voltage at the USB hub regulated on the RPi3B?
Replies: 7
Views: 375

Re: Is the voltage at the USB hub regulated on the RPi3B?

It is directly connected. Not to the '5V source' it isn't as klricks notes. It goes through the polyfuse and 'ideal diode' if powered through the micro-USB, and goes through the USB power control chip as well, even if power is sourced via the GPIO connector. But it is pretty much 'what goes in is w...
by davidcoton
Sat Sep 15, 2018 9:50 am
Forum: Advanced users
Topic: Is the voltage at the USB hub regulated on the RPi3B?
Replies: 7
Views: 375

Re: Is the voltage at the USB hub regulated on the RPi3B?

Using the RPI3b. I know that it should be 5V, but is it directly connected to the source? If the source goes to 5.5V, will the USB hub on the Pi also provide 5.5V or is it regulated down to 5V? It is directly connected. The spec limit for voltage input is 5V +/- 0.25V, so 5.5V is out of spec. AIUI ...
by davidcoton
Sat Sep 15, 2018 9:48 am
Forum: Beginners
Topic: Illuminated push button
Replies: 41
Views: 758

Re: Illuminated push button

B.Goode wrote:
Sat Sep 15, 2018 9:38 am
Maybe the description "12v switch" is an indication of the maximum voltage that the switch component can safely handle?
@tlfong01quoted the relevant line of the spec, but in de-duplicating his post has since deleted it.
Switch Rating: 2A 36V
[Edit] And since replaced....
by davidcoton
Fri Sep 14, 2018 9:27 pm
Forum: General discussion
Topic: any way to fix the microSD card reader on the P3b+?
Replies: 10
Views: 328

Re: any way to fix the microSD card reader on the P3b+?

EDIT: this may not be relevant if all your Pis are Pi3B+ Not all images will work on a Pi3B+. Try a new download of the latest Raspbian. Older Raspbian Stretch images can be updated on an older Pi: sudo apt update sudo apt full-update Older Raspbian (Jessie, Wheezy) and other OSs are more tricky -- ...
by davidcoton
Thu Sep 13, 2018 11:22 pm
Forum: Troubleshooting
Topic: Low voltage warning with 3B+ and 7 inch touch screen
Replies: 5
Views: 157

Re: Low voltage warning with 3B+ and 7 inch touch screen

I also found that problem with an older Pi B+ and official touchscreen. In the end I found a dual output USB PSU (2x 2.4A)and used two USB cables for power. The low voltage warning occurs long before the Pi runs out of volts, but other USB peripherals and possibly HDMI might be affected. However, yo...
by davidcoton
Thu Sep 13, 2018 11:14 pm
Forum: General discussion
Topic: MCP3008 readings
Replies: 162
Views: 2783

Re: MCP3008 readings

We agree in the end. As you say, better safe than sorry. It will be better to buy a clamp meter with a digital output, that takes care of all the safety issues. A quick Google found several with USB (which may or may not be easy to use with a Pi, or even any other Linux system), but I can't make any...
by davidcoton
Thu Sep 13, 2018 9:55 pm
Forum: General discussion
Topic: MCP3008 readings
Replies: 162
Views: 2783

Re: MCP3008 readings

-- On the plus side, the ACS712 can do the job. -- Well, I disagree with this answer. This device is not fully save* to use it in this case. And I will give a detailed explanation in a couple of hours, why (I think) this is the case. I will re-phrase -- On the plus side, the ACS712 can do the job w...
by davidcoton
Thu Sep 13, 2018 2:14 pm
Forum: General discussion
Topic: MCP3008 readings
Replies: 162
Views: 2783

Re: MCP3008 readings

1. If I want to measure 1 A to 30 A. Do I need any other part in circuit to measure 30 A DC current ? I don't think because I have seen some arduino based circuit they don't use any extra parts 2. sensor can sense AC or DC current so if i replace DC battery with AC main Is that circuit capable to m...
by davidcoton
Tue Sep 11, 2018 10:02 pm
Forum: Advanced users
Topic: How to use SC16IS752???
Replies: 7
Views: 186

Re: How to use SC16IS752???

6by9 wrote:
Tue Sep 11, 2018 10:07 am
If it is, then
... something has fallen off the end of your message?
by davidcoton
Tue Sep 11, 2018 9:23 pm
Forum: General discussion
Topic: Pi to Pi communication
Replies: 10
Views: 321

Re: Pi to Pi communication

First, as others have said, do not connect the 3V3 supplies. Each Pi will generate it's own 3V3, if they are not exactly the same (and they probably aren't) they will fight, which can crash a Pi. Just supply the GPS from one Pi. Second, do not connect the 5V supplies. At best unnecessary if each Pi ...
by davidcoton
Tue Sep 11, 2018 9:01 pm
Forum: General discussion
Topic: Getting Live Voltage data from Pi 3B+
Replies: 8
Views: 234

Re: Getting Live Voltage data from Pi 3B+

As @Paul Hutch says. Look at some sample A2D circuits, as often fouund in data sheets. The reference voltage is usually the maximum reading of the A2D. It must be stable, and independent of what you want to measure. Somewhere on this site is an example where someone used the 5V supply they wanted to...
by davidcoton
Mon Sep 10, 2018 10:26 pm
Forum: General discussion
Topic: Getting Live Voltage data from Pi 3B+
Replies: 8
Views: 234

Re: Getting Live Voltage data from Pi 3B+

The LM385 provides the reference voltage for the A2D. It is not altering the Pi's supply voltage.
The reference voltage must be as stable as possible to order for the measurements to be meaningful.
by davidcoton
Mon Sep 10, 2018 8:20 pm
Forum: General discussion
Topic: Getting Live Voltage data from Pi 3B+
Replies: 8
Views: 234

Re: Getting Live Voltage data from Pi 3B+

The A/D won't make much difference to tthe current used, and therefore to the PSU voltage. The display module might make more difference. The important thuing is that you must not use the Pi 5V as a voltage reference -- that will make the rsult constant! You can use the 5V to supply a voltage refere...
by davidcoton
Mon Sep 10, 2018 9:41 am
Forum: General discussion
Topic: MCP3008 readings
Replies: 162
Views: 2783

Re: MCP3008 readings

I broke my charger Send it for recycling. Once open like that, you can't safely use it. I read the datasheet but I don't know what's the maximum current it can give at output pi How do you expect anyone else to know if the information is not in the datasheet? Once again, you are forgetting the effe...
by davidcoton
Mon Sep 10, 2018 9:21 am
Forum: General discussion
Topic: Wired Heating/Cooling Theremostat
Replies: 4
Views: 123

Re: Wired Heating/Cooling Theremostat

Would it be possible to upgrade a 10-year old wired Honeywell heating and cooling thermostat with a wifi function? Yes. The simplest and (probably) cheapest way would be to find a suitable commercial product. Other advantages may include reliability and appearance. On the other hand, the DIY route ...
by davidcoton
Mon Sep 10, 2018 9:11 am
Forum: General discussion
Topic: STICKY: PINN - An enhanced version of NOOBS.
Replies: 583
Views: 121630

Re: STICKY: PINN - An enhanced version of NOOBS.

I also think that @procount should add disable_overscan=1 option in PINN's config.txt file as default The default must be the "safe" option, the one that will not put anything off screen, under any circumstances. I don't know if your proposed setting would risk that, but if it does, it's a non-star...
by davidcoton
Sun Sep 09, 2018 2:08 pm
Forum: Troubleshooting
Topic: booting problem: end kernel panic - not syncing
Replies: 9
Views: 226

Re: booting problem: end kernel panic - not syncing

I think Dougie is trying to say, DON'T use rpi-update, because it may install unstable versions of some programs. The correct incantation for normal upgrades is: sudo apt update sudo apt upgrade Sometimes you need a bit more , so you can use: sudo apt update sudo apt full-upgrade Both of these shoul...
by davidcoton
Sun Sep 09, 2018 2:00 pm
Forum: General discussion
Topic: MCP3008 readings
Replies: 162
Views: 2783

Re: MCP3008 readings

@danjperron @brandon92 I think @Fan174 has realised that s/he is not ready to test anything at between 2 and 30A, and that the previous mA tests would not work. So now we have an achievable test at the bottom end of the range given by the ACS712 ad MCP3008 combination, which will prove the concept. ...
by davidcoton
Sun Sep 09, 2018 1:46 pm
Forum: Beginners
Topic: Raspberry(3b+)-PCA9685-12V Fans
Replies: 32
Views: 535

Re: Raspberry(3b+)-PCA9685-12V Fans

But it dont work. We can't work out why not, and therefore what is wrong, from that. What bit didn't work? How did you check and test your circuit? Could you read the temp sensor? Did you produce a PWM signal? Did the fan turn at all? What program did you use to convert temperature to PWM? (Post it...
by davidcoton
Sun Sep 09, 2018 1:36 pm
Forum: General discussion
Topic: MCP3008 readings
Replies: 162
Views: 2783

Re: MCP3008 readings

In first test I will connect 10 ohms resistor then I will calculate current throw resistor Have you done the power calculation on that? 5V through 10R gives 0.5A. 5V at 05.A gives 2.5W. What is the power rating of your resistor? If you don't know, you have a problem. Even if the resistor is adequat...
by davidcoton
Sun Sep 09, 2018 11:50 am
Forum: General discussion
Topic: MCP3008 readings
Replies: 162
Views: 2783

Re: MCP3008 readings

OK, that makes more sense. But where is the power going?
5V 0.2A is 1 Watt. 5V 2A is 10 Watts. Most potentiometers will not survive that.
by davidcoton
Sun Sep 09, 2018 10:41 am
Forum: General discussion
Topic: MCP3008 readings
Replies: 162
Views: 2783

Re: MCP3008 readings

I will use this sentence in my own language "je jette l'éponge". @Fan174, I think I agree. I do not think you understand what you are doing, and not just because of language problems. Where do you want to measure +/- 30A? That is a LOT of current. You need VERY careful wiring with THICK wire for th...

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