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by grahamed
Sat Feb 28, 2015 5:28 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: 5v relay board adaptation
Replies: 4
Views: 981

Re: 5v relay board adaptation

Hi

I see there is a transistor on the board already, and a 1k resistor - although I cannot see how it helps with only two input terminals....
by grahamed
Sat Feb 28, 2015 5:24 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: 5v relay board adaptation
Replies: 4
Views: 981

Re: 5v relay board adaptation

Hi

A push button to what? Active whilst pushed or push-on, push-off?

In any case you will need a FET or BJT between the GPIO and the relay for each relay. This forum is full of such things.
by grahamed
Sat Feb 28, 2015 5:15 pm
Forum: Automation, sensing and robotics
Topic: help wiring up power relay bars
Replies: 26
Views: 3637

Re: help wiring up power relay bars

Hi I suspect there is some confusion about all these power supplies/rails/VCCs. 1) 5V to the Pi and the 23017 - needs to be approx 1A (a bit more for Pi2) - the Pi I2C pins can stand 5V if I remember correctly. 2) 5V to the opto-inputs. Each LED needs 15-20mA, so 8 x 20mA = 160mA. Can be connected t...
by grahamed
Sat Feb 28, 2015 4:48 pm
Forum: Automation, sensing and robotics
Topic: help wiring up power relay bars
Replies: 26
Views: 3637

Re: help wiring up power relay bars

Hi IMHO it is unlikely that a big PSU would be unable to supply a small load. Not impossible, just unlikely. I have seen PSUs that provide too much voltage on too little load - poor regulation - and a few that switched off when the voltage went high due to too little load. Is the PSU switching off? ...
by grahamed
Sat Feb 28, 2015 4:11 pm
Forum: Automation, sensing and robotics
Topic: HOW-TO Build an Automatic Power Supply for the Pi
Replies: 39
Views: 44512

Re: HOW-TO Build an Automatic Power Supply for the Pi

Hi Very nice. A bit back I made a PSU/control unit myself. I seem to have lost most of the work but maybe this bit would be of interest to someone. Clipboard03.jpg The pic shows a perfect diode at the top, and a perfect diode with disable at the bottom. The 5V input, if present, will pass straight t...
by grahamed
Wed Feb 25, 2015 10:37 pm
Forum: Automation, sensing and robotics
Topic: Current sensing
Replies: 3
Views: 8348

Re: Current sensing

Hi One thing to note, all current transformers have a maximum rating obviously. Less obviously they have a minimum rating - below maybe 5% of rating they may produce little or no output due to hysteresis in the core. So choose your rating with care. Also take notice of the need for termination as me...
by grahamed
Wed Feb 25, 2015 9:59 pm
Forum: Automation, sensing and robotics
Topic: Hacking a SuperSwitch?
Replies: 5
Views: 1149

Re: Hacking a SuperSwitch?

Hi again

Having had a look at various 2262 based remotes I'd say it was a 12V and the French says it may explode if recharging is attempted....it also looks a bit dumpy for a AA or AAA.

Anyway the point was that 12v or 1v5 makes difference to the resistors.
by grahamed
Wed Feb 25, 2015 9:36 pm
Forum: Automation, sensing and robotics
Topic: 433 MHz debugging? (Raspberry-Strogoganoff)
Replies: 20
Views: 3844

Re: 433 MHz debugging? (Raspberry-Strogoganoff)

you honour me too much.....
by grahamed
Wed Feb 25, 2015 1:08 pm
Forum: Automation, sensing and robotics
Topic: help wiring up power relay bars
Replies: 26
Views: 3637

Re: help wiring up power relay bars

Hi I don't like to sound negative but a picture is worth a thousand words - really - without a diagram it is almost impossible to diagnose the problem or to make specific suggestions. and do you have a circuit for the board? Do you know how to test it? If it were me doing this I'd do this: - remove ...
by grahamed
Wed Feb 25, 2015 12:07 pm
Forum: Automation, sensing and robotics
Topic: 433 MHz debugging? (Raspberry-Strogoganoff)
Replies: 20
Views: 3844

Re: 433 MHz debugging? (Raspberry-Strogoganoff)

Hi My £1 USB sound card came from eBay. Interesting? I think maybe you are reading more than I am saying - I am not making myself clear as usual. I mean I removed the case from the sound card card and soldered wires to the incoming 5V and zero, and then connected these to bit of strip board with a 4...
by grahamed
Wed Feb 25, 2015 10:42 am
Forum: Automation, sensing and robotics
Topic: 433 MHz debugging? (Raspberry-Strogoganoff)
Replies: 20
Views: 3844

Re: 433 MHz debugging? (Raspberry-Strogoganoff)

Hi I find that my FM radio picks up interference form the 433/315 transmitters if they are close. Not accurate but I can hear at least something is being transmitted. I also have 315 and 433 receivers with a LED on the output - no Tx they flicker randomly, on TX you can see a brief "organised" flash...
by grahamed
Fri Feb 13, 2015 8:39 pm
Forum: Troubleshooting
Topic: Pi2 missing on-screen characters and elements
Replies: 0
Views: 235

Pi2 missing on-screen characters and elements

Hi I have a Pi2 running a SD previously in a Pi (actually it's an image cloned onto a microSD using parted and DD in case that makes any difference - new card was smaller than previous) upgraded on Pi and then on Pi2. It's much, much snappier and all is well except for one weird thing - when I move ...
by grahamed
Sat Feb 07, 2015 5:38 pm
Forum: Automation, sensing and robotics
Topic: convert Hz to mA
Replies: 6
Views: 3222

Re: convert Hz to mA

Hi Continuing the honourable tradition of answering a question wih a question - Although I am sure a RPi can do frequency to PWM, and then an RC will do PWM to voltage, how about an LM2907 (<£2 on ebay) to do the frequency to voltage? Voltage to current can be as simple as a single OPA but if you wa...
by grahamed
Sun Jan 25, 2015 10:14 pm
Forum: Automation, sensing and robotics
Topic: Measuring large resistance ranges with a Pi
Replies: 7
Views: 1601

Re: Measuring large resistance ranges with a Pi

Hi Use a 555? Using a low-leakage cap is good, but on the other hand the sheet shows (chip) discharge leakage (at 12V supply) = 1nA to 100nA. Now 1nA and 55G ohm is 55V, and 55G and 100nA is 5.5kV. To put this another way you'd need to supply RA (on the sheet) with between 55V and 5.5kV to cancel th...
by grahamed
Thu Jan 15, 2015 9:21 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Breadboard-friendly logic level shifters with strong out
Replies: 7
Views: 3706

Re: Breadboard-friendly logic level shifters with strong out

Hi

Dr Google tells me that APA102 use 5V SPI, so maybe Adafruit level-shifters would be a good idea?
by grahamed
Thu Jan 15, 2015 9:10 pm
Forum: Automation, sensing and robotics
Topic: 433Mhz RC Outlets known to work with rcswitch-pi
Replies: 5
Views: 3207

Re: 433Mhz RC Outlets known to work with rcswitch-pi

Hi Any number of people, using many different methods, have managed to control sockets using 2262. Look around the forum. Perhaps a little more info about the problem, what you have done so far, what sockets they are, what the "clear differences" are.......etc. and people might be able to help I thi...
by grahamed
Wed Jan 07, 2015 5:29 pm
Forum: Automation, sensing and robotics
Topic: How to know the state of a switch connected to mains
Replies: 12
Views: 2512

Re: How to know the state of a switch connected to mains

Hi A problem with the "give Pi complete control" approach is that the Pi MUST be there and working at ALL times. Failure to comply reduces the spousal acceptance factor hugely. The "two-way circuit where one switch is a Pi-controlled relay" approach leaves the possibility of manual control at need. ...
by grahamed
Tue Jan 06, 2015 7:48 pm
Forum: Automation, sensing and robotics
Topic: How to know the state of a switch connected to mains
Replies: 12
Views: 2512

Re: How to know the state of a switch connected to mains

Hi all This question has appeared many times on this forum. The OP specifies knowing the state of the switch but most replies do not address this. Micronauts, on the other hand, does address it and I would add - 3) voltage sensor - probably easier to add than current sensor (but not as sure - maybe ...
by grahamed
Fri Jan 02, 2015 7:54 pm
Forum: Automation, sensing and robotics
Topic: Dimming the lights (MOSFET + digi pot)
Replies: 10
Views: 5920

Re: Dimming the lights (MOSFET + digi pot)

Hi

So basically there are no acceptable phase controllers on eBay at the moment.
by grahamed
Thu Jan 01, 2015 7:13 pm
Forum: Automation, sensing and robotics
Topic: Dimming the lights (MOSFET + digi pot)
Replies: 10
Views: 5920

Re: Dimming the lights (MOSFET + digi pot)

Hi If on/off is sufficient then a relay, SSR or otherwise would seem to suit, but the first post the digital pot is controls the brightness of the light. seems to be about dimming. Ready built controlled dimmers/controllers seem to be a bit rare; I could find only one on eBay - http://www.ebay.co.uk...
by grahamed
Sat Dec 27, 2014 5:20 pm
Forum: Automation, sensing and robotics
Topic: 1 Channel relay and GPIO
Replies: 13
Views: 4260

Re: 1 Channel relay and GPIO

Hi Following all this with some interest.... It sounds as though the current through the coil when GPIO is 3V3 is sufficient to hold the relay in but I guess probably not enough to pull it in? A 1V7 relay would be sensitive indeed. Are you sure the pin is in fact switching? Is there a diode on the p...
by grahamed
Fri Dec 26, 2014 2:38 pm
Forum: Automation, sensing and robotics
Topic: How to read 64 analog signals at the same time.
Replies: 13
Views: 6428

Re: How to read 64 analog signals at the same time.

Hi If cost is an issue CD4051 is cheap. On channel resistance is 80R (for 15V supply) why is this a problem? Are the signals d.c (or at least very low frequency), or can we assume a minimum frequency? x100 d.c. is hard, x100 a.c. is easy. Strain gauges (if indeed that is what we are dealing with) ar...
by grahamed
Fri Dec 26, 2014 2:26 pm
Forum: Automation, sensing and robotics
Topic: receiving 433mhz on gpio daemon script
Replies: 33
Views: 10913

Re: receiving 433mhz on gpio daemon script

Hi Much has been posted about 433MHz receivers, many have given up on them. A problem with most of (maybe all) the cheapo ones is that, when not receiving a signal they output a continuous stream of random high and low due to the AGC action, typically at a higher frequency than the valid high-low cy...
by grahamed
Thu Nov 27, 2014 7:58 pm
Forum: Automation, sensing and robotics
Topic: Hacking a SuperSwitch?
Replies: 5
Views: 1149

Re: Hacking a SuperSwitch?

Hi

Might I ask what is the battery voltage?

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