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by NGC6543
Sun Mar 24, 2019 6:50 pm
Forum: Other projects
Topic: Simplest UPS for RPi
Replies: 3
Views: 547

Re: Simplest UPS for RPi

This is a quick design off the top of my head based on what I think I have in my bits in the loft. I've changed the design to a 12V PSU and 7.2V NiMH pack (6 cells). I don't need hours of runtime and that should give enough juice to run the Pi short-term. The output is intended to drive a 5V switchi...
by NGC6543
Sun Mar 24, 2019 1:48 am
Forum: Other projects
Topic: Simplest UPS for RPi
Replies: 3
Views: 547

Simplest UPS for RPi

I bought my first RPi (3B+) to run PiHole and a few other simple services on my LAN. Having had a few power cuts recently, I'm a bit paranoid about the SD/SSD getting corrupted if it happens again. That's mostly because it is going to live in the loft where my network rack is and it's a pain to get ...
by NGC6543
Sat Mar 23, 2019 12:51 am
Forum: General discussion
Topic: Sterilization of Pi
Replies: 27
Views: 1662

Re: Sterilization of Pi

I don't think a charged capacitor is your real (potential) problem. If you're using ethylene oxide (that's the usual suspect), you should be using a process to ensure a non-explosive environment in the chamber. EtO requires about 3% air to form a combustible mixture. The process needs to remove air ...
by NGC6543
Thu Mar 21, 2019 7:04 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: More than two HW PWMs
Replies: 7
Views: 406

Re: More than two HW PWMs

This is begging for an FPGA or CPLD solution. A CPLD like an Altera EPM240 could generate all 13 frequencies from a master clock using dividers, and maybe even have enough logic left over to make output multiplexers to route the clocks as required onto the eight channels. I think that's probably eas...
by NGC6543
Mon Mar 18, 2019 6:57 pm
Forum: Troubleshooting
Topic: Stuck setting up clock for nonstandard ADC
Replies: 36
Views: 1572

Re: Stuck setting up clock for nonstandard ADC

Not sure, but check that the returned handle (for the second one especially) is >=0. <0 means an error in setting it up.

There's no need to set it up twice though. Once it's open, it's open.
by NGC6543
Mon Mar 18, 2019 3:27 pm
Forum: Troubleshooting
Topic: Stuck setting up clock for nonstandard ADC
Replies: 36
Views: 1572

Re: Stuck setting up clock for nonstandard ADC

Channel refers to which Chip Enable line (CEx) line is going to be used for that particular SPI configuration. The returned Handle is then used to refer to that SPI device in subsequent commands. Having the initialisation command return a Handle is a standard way of doing things like this with inter...
by NGC6543
Sun Mar 17, 2019 11:07 pm
Forum: Automation, sensing and robotics
Topic: Best way to get reading from hundreds of LDRs into RPi?
Replies: 15
Views: 1500

Re: Best way to get reading from hundreds of LDRs into RPi?

Folks on the 'net have made similar things by moving the sensor itself across the image plane. I always liked the old way of decapping a DRAM chip... but that might just be classed as using a camera sensor. I used to have a musty old book with detailed plans to make a mechanical television camera an...
by NGC6543
Sun Mar 17, 2019 9:50 pm
Forum: Troubleshooting
Topic: Stuck setting up clock for nonstandard ADC
Replies: 36
Views: 1572

Re: Stuck setting up clock for nonstandard ADC

As I mentioned, I'm completely new (as in, had one for two weeks) to the RPi so I can't advise on programming it or if a bit-banging solution would work on the Pi. With an MCU, which I am used to, this would be a trivial task. I've had a quick look at the development board's schematic and, while the...
by NGC6543
Sun Mar 17, 2019 9:05 pm
Forum: Automation, sensing and robotics
Topic: Best way to get reading from hundreds of LDRs into RPi?
Replies: 15
Views: 1500

Re: Best way to get reading from hundreds of LDRs into RPi?

Well, it's your school project ;) so I'm not going to say much more, but I'll give a few hints: First, I made an error - the digital multiplexer should say de multiplexer (or decoder). Something like a 74HCT154 (which is 16 bits - you could cascade two for more bits, or find a bigger one). It's just...
by NGC6543
Sun Mar 17, 2019 8:42 pm
Forum: Automation, sensing and robotics
Topic: Best way to get reading from hundreds of LDRs into RPi?
Replies: 15
Views: 1500

Re: Best way to get reading from hundreds of LDRs into RPi?

Hmm... I can envisage a matrix of LDRs. Let's say the LDRs have terminals A and B: Each row of LDRs has all the A pins connected to an output of a digital multiplexer demultiplexer/decoder, so that each row can have a voltage applied to all LDRs in that row. The LDR B pins in each column are connect...
by NGC6543
Sun Mar 17, 2019 7:47 pm
Forum: Automation, sensing and robotics
Topic: Best way to get reading from hundreds of LDRs into RPi?
Replies: 15
Views: 1500

Re: Best way to get reading from hundreds of LDRs into RPi?

That's quite a project! You need to give more specifications, for instance: How much (digital) resolution do you need? (That chip you linked is ten bits; would eight bits do?) How frequently do you need to sample? (Samples per second/minute/hour.) How are you 'reading' the LDRs? (As a potential divi...
by NGC6543
Sun Mar 17, 2019 7:19 pm
Forum: Troubleshooting
Topic: Stuck setting up clock for nonstandard ADC
Replies: 36
Views: 1572

Re: Stuck setting up clock for nonstandard ADC

I don't know what's going on with your circuit, but I think you misunderstand the "10 clock cycles" issue. At least, it sounds like it from your comments. It might not make any actual difference to what you are doing, but... The ADC starts its conversion process at CS0's falling edge. It's a Success...
by NGC6543
Sat Mar 16, 2019 7:02 pm
Forum: Beginners
Topic: Input Relays
Replies: 21
Views: 1315

Re: Input Relays

Check out the RM84 series relays, for instance: RM84-2012-35-5110. I've not used that particular one but it seems to fit your requirements, and is quite small and inexpensive (for an AC-coil relay). A relay does seem the simplest solution. As to the optocoupler method, there's a page explaining how ...
by NGC6543
Sat Mar 16, 2019 4:31 pm
Forum: Other projects
Topic: Power for outoor enclosure
Replies: 4
Views: 865

Re: Power for outoor enclosure

I've no idea what the electrical regulations are where you are, and whether you can be prosecuted for not following them, but in the UK we have to be careful to comply with them. That gets a little more complicated when going outdoors. While I'm familiar with the above, and have laid armoured cable ...
by NGC6543
Mon Mar 11, 2019 3:58 am
Forum: Troubleshooting
Topic: Stuck setting up clock for nonstandard ADC
Replies: 36
Views: 1572

Re: Stuck setting up clock for nonstandard ADC

Your compile errors are because you are linking two, conflicting libraries. wiringpi.h and bcm2835.h probably aren't intended to be used together. Notice that they both declare delayMicroseconds, but in different ways (I looked at the .h codes... one declares it as the variable itself, the other as ...
by NGC6543
Sun Mar 10, 2019 10:00 pm
Forum: General discussion
Topic: LiPo Battery Voltage Drops
Replies: 7
Views: 430

Re: LiPo Battery Voltage Drops

I think there's some misunderstanding about this "4 Amp" value, maybe with the manufacturers of the board. I believe that value is the switch current maximum (i.e. the maximum current supplied from the battery to the inductor during energising), not the output current from the regulator. If we look ...
by NGC6543
Sun Mar 10, 2019 9:40 pm
Forum: Beginners
Topic: Choosing a device for analog
Replies: 7
Views: 390

Re: Choosing a device for analog

Is the gear change cable open, and if so (or even if not) might it be simpler to have a linear position sensor on it?

Maybe something like a slider potentiometer with the slider pinned to the cable.
by NGC6543
Sun Mar 10, 2019 3:43 pm
Forum: Off topic discussion
Topic: Where's the "New Posts" link gone?
Replies: 3
Views: 609

Re: Where's the "New Posts" link gone?

Thank you. Changing back to RPi didn't bring back the links, but I prefer pro-silver so I'll leave it on that.

Problem solved, one way or another :lol:
by NGC6543
Sun Mar 10, 2019 2:39 pm
Forum: Off topic discussion
Topic: Where's the "New Posts" link gone?
Replies: 3
Views: 609

Where's the "New Posts" link gone?

...or am I losing the plot? I'm sure there was a link to New Posts/Your Posts/Etc., where I've indicated with a green circle in the picture below. Since yesterday, it isn't there. I keep clicking on empty space. I've tried different browsers, whitelisted the site in my tracking blocker and even reve...
by NGC6543
Wed Mar 06, 2019 2:37 pm
Forum: HATs and other add-ons
Topic: What i/o is used by the TV HAT ?
Replies: 5
Views: 1891

Re: What i/o is used by the TV HAT ?

Thank you!

My TV HAT has arrived just now, so it's time to play.
by NGC6543
Wed Mar 06, 2019 2:09 pm
Forum: HATs and other add-ons
Topic: What i/o is used by the TV HAT ?
Replies: 5
Views: 1891

What i/o is used by the TV HAT ?

I'm awaiting arrival of my TV HAT today, and I can't find any information about what bits of the interface it uses. I would have thought this would be readily available; perhaps I'm missing it somewhere. Does anyone know what pins are used? I want to add a few other bits (like a DIY battery-UPS with...
by NGC6543
Tue Mar 05, 2019 5:33 pm
Forum: Advanced users
Topic: Ping sweep of my network
Replies: 15
Views: 1017

Re: Ping sweep of my network

Assuming we stick to the simple ping method in the OP, wouldn't a simple bash script be the most efficient way? Something like this: (Please note that I write bash scripts about as often as I jump off tall buildings without an umbrella, plus I'm a complete newcomer to the Pi, so please feel free to ...
by NGC6543
Tue Mar 05, 2019 1:36 pm
Forum: Networking and servers
Topic: How to build undetectable ethernet sniffer?
Replies: 8
Views: 2595

Re: How to build undetectable ethernet sniffer?

I used to keep an old hub for just such a purpose. Still limited to 10/100 though. You can now buy a five port, managed, gigabit switch that does port mirroring for around £22 / US$30. Netgear, TP-Link and Zyxel do them, and probably others. Just insert that into the link. That's the cheapest way to...
by NGC6543
Tue Mar 05, 2019 1:39 am
Forum: Networking and servers
Topic: How to build undetectable ethernet sniffer?
Replies: 8
Views: 2595

Re: How to build undetectable ethernet sniffer?

@bzt, that will only capture packets forwarded out of that switch port. It only worked for you because the Cisco switch was configured with a SPAN port (your mirroring port) which explicitly copied packets from one or more other interfaces out of the SPAN port for you to capture. I have a similar se...
by NGC6543
Sat Mar 02, 2019 2:11 am
Forum: Networking and servers
Topic: How to build undetectable ethernet sniffer?
Replies: 8
Views: 2595

Re: How to build undetectable ethernet sniffer?

Since the Pi only has one Ethernet port, you can only capture one traffic direction because only the interface has only one 'receiver'. I found a diagram on this page (quicker than drawing one for you): https://www.instructables.com/id/Ethernet-Tap/ You'll have to decide which side you want to monit...

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