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by NGC6543
Sun Mar 31, 2019 1:26 pm
Forum: Automation, sensing and robotics
Topic: How best to control higher voltage relays with 12v/24v coils?
Replies: 26
Views: 3514

Re: How best to control higher voltage relays with 12v/24v coils?

Hey NGC6543, would it be possible to use these Darlington arrays? Yes, but you have no optical isolation with those. Plus they'll drop about 1.4V from your relay supply but that shouldn't stop your relays working. I would feel uncomfortable with not having the isolation myself. Things do occasional...
by NGC6543
Sat Mar 30, 2019 7:43 pm
Forum: Automation, sensing and robotics
Topic: How best to control higher voltage relays with 12v/24v coils?
Replies: 26
Views: 3514

Re: How best to control higher voltage relays with 12v/24v coils?

First... the problem with using big SSRs to switch the PSUs directly is that the SSRs leak current when off and connected to an AC supply. This is because they contain a snubber circuit on the output. This leakage will slowly charge the capacitors in the PSU and cause it to cycle on every time the c...
by NGC6543
Fri Mar 29, 2019 9:49 pm
Forum: Automation, sensing and robotics
Topic: How best to control higher voltage relays with 12v/24v coils?
Replies: 26
Views: 3514

Re: How best to control higher voltage relays with 12v/24v coils?

There certainly are better ways if you're open to some soldering. I would use an opto coupler to drive a MOSFET, to drive the relay. Alternatively you could use a MOSFET photorelay which is an optocoupler with a MOSFET 'output' in one little package. For instance the TLP172A will happily run off a G...
by NGC6543
Fri Mar 29, 2019 3:57 pm
Forum: Automation, sensing and robotics
Topic: Wiring relay to Pi
Replies: 27
Views: 3700

Re: Wiring relay to Pi

I agree with PhatFil. Pulling the LEDs might well solve the issue by lowering the current required; depends if they used low current (2mA) LEDs or not. The relay is driven through the transistor that can be seen on the board. My guess is the transistor is connected common collector, rather than in t...
by NGC6543
Thu Mar 28, 2019 9:32 am
Forum: General discussion
Topic: What Power supply to power Raspberry + 10inch screen + LED Light
Replies: 3
Views: 266

Re: What Power supply to power Raspberry + 10inch screen + LED Light

The specs for that panel and driver are a bit vague; I bet it doesn't actually need 12V*2A=24W. Likewise, your LED light... 5V*1A=5W is a very bright LED. It's enough to fully light a small room. Still, we'll work with those values: For the 5V parts, you need 2A for the Raspberry plus 1A for the LED...
by NGC6543
Tue Mar 26, 2019 8:53 pm
Forum: Beginners
Topic: Using RPi to spoof ISP gateway
Replies: 4
Views: 344

Re: Using RPi to spoof ISP gateway

I'll swallow my jealousy of your gigabit internet... I've not head of an ISP doing that. At first thought, it sounds to me like you need a basic router (or router OS on an SBC) that does overloaded NAT (usually just called NAT on consumer routers; they all do it). But it might be more complicated, d...
by NGC6543
Sun Mar 24, 2019 6:50 pm
Forum: Other projects
Topic: Simplest UPS for RPi
Replies: 3
Views: 749

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: 749

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: 2382

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: 629

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: 2133

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: 2133

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: 1989

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: 2133

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: 1989

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: 1989

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: 1989

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: 2133

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: 1853

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: 1273

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: 2133

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: 674

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: 545

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: 760

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: 760

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...

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