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by grahamed
Fri Dec 18, 2015 8:20 pm
Forum: Automation, sensing and robotics
Topic: Circuit pictures- or circuit diagrams?
Replies: 10
Views: 2456

Re: Circuit pictures- or circuit diagrams?

Hi I use Eagle. The free version is ........free, though the pcb layout tool is very restricted, but then you don't have to use it. A simple circuit takes a few minutes and you can export the image as jpg. Eagle has a good range of components out-of-the-box, and defining your own schematic symbols i...
by grahamed
Sun Dec 06, 2015 3:32 pm
Forum: Automation, sensing and robotics
Topic: Multichannel RF communication
Replies: 6
Views: 1951

Re: Multichannel RF communication

Hi

Have a look at http://randomnerdtutorials.com/esp8266-web-server/

Should be all you need.
by grahamed
Tue Dec 01, 2015 8:49 pm
Forum: Automation, sensing and robotics
Topic: Multichannel RF communication
Replies: 6
Views: 1951

Re: Multichannel RF communication

Hi I use NRF24l01+ with Arduino (thence to Pi over serial because Arduino came first) but you can drive it from Pi. Much, much better than any 433MHz stuff I have tried. Thety come in several power grades with PCB aerials or rubber ducks for longer range. Also ESP8266 use wifi, either as a wifi stac...
by grahamed
Sat Nov 28, 2015 11:42 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Rs232 to TTL with handshaking
Replies: 4
Views: 1239

Re: Rs232 to TTL with handshaking

Hi I think that there might be a problem further down the line if there is no flow-control, but the problem the OP has at this time in no flow, not loss of characters. If the Max232 is doing its job then the voltage levels should be adequate - can this be confirmed? That it does loop-back is a good ...
by grahamed
Tue Nov 24, 2015 8:19 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Rs232 to TTL with handshaking
Replies: 4
Views: 1239

Re: Rs232 to TTL with handshaking

Hi Back in the day when RS232 data would not flow we connected RTS-CTS and DSR, DCD and DTR over-riding the handshaking. I mean connecting 4-5 and 6-8-20 (on DB25) on the interface and on both sides if both sides had handshaking. So we ended up with only 3 wires across the interface - crossed 2-3, 3...
by grahamed
Tue Nov 17, 2015 4:08 pm
Forum: Automation, sensing and robotics
Topic: Best SSR kit
Replies: 14
Views: 2461

Re: Best SSR kit

The schematic for http://www.sainsmart.com/8-channel-5v-solid-state-relay-module-board-omron-ssr-4-pic-arm-avr-dsp-arduino.html indicates that it is non-inverting and will be - on when the GPIO is high off when the GPIO is low, or the Pi is off, or the Pi is disconnected. In general you cannot say t...
by grahamed
Mon Nov 16, 2015 10:05 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: False reads from GPIO
Replies: 11
Views: 1413

Re: False reads from GPIO

Surely it does need a correct circuit, and the first and second replies provided such a thing. Specifically as original set up it cannot work. The first reply offers two alternative acceptable topologies, and the second offers an improved version of one of these and with a further suggestion to add ...
by grahamed
Mon Nov 16, 2015 5:33 pm
Forum: Automation, sensing and robotics
Topic: Pi-Mote and Energenie sockets
Replies: 1
Views: 578

Re: Pi-Mote and Energenie sockets

Hi The energenie system seems to be a pretty standard implementation. A single hand remote can control a maximum of 4 learning sockets; on or off for individual sockets plus all off. If I remember rightly this is exactly like the "Status" branded ones. I'd guess they are inter-operable. Have you add...
by grahamed
Mon Nov 16, 2015 5:03 pm
Forum: Automation, sensing and robotics
Topic: Best SSR kit
Replies: 14
Views: 2461

Re: Best SSR kit

This one does not seem to be invertinghttp://www.sainsmart.com/8-channel-5v-s ... duino.html
by grahamed
Fri Oct 09, 2015 3:55 pm
Forum: Automation, sensing and robotics
Topic: Using the Pi with ADT panel
Replies: 1
Views: 2082

Re: Using the Pi with ADT panel

Hi I don't think I can help with that specific panel but I can describe a few of the things I did when interfacing my ADT alarm panel. - details at http://www.wavertreeelec.co.uk/skin/frontend/target/target/pdfs/Optima_Compact_Accenta_Panels.pdf might help you or give others ideas. First I wanted th...
by grahamed
Wed Sep 23, 2015 9:11 pm
Forum: Automation, sensing and robotics
Topic: Bulb sensor
Replies: 5
Views: 956

Re: Bulb sensor

Hi If you want an electronic version. bulb sensor.jpg Output is low when lamp draws current. R2 (sense) chosen to drop 1V at 80% of nominal lamp current. R1 (lamp) represents the lamp itself. R2 and R3 are in no way critical. T1 can be almost any low or medium power npn BJT. It could even be this fo...
by grahamed
Wed Sep 23, 2015 7:25 pm
Forum: Automation, sensing and robotics
Topic: Bulb sensor
Replies: 5
Views: 956

Re: Bulb sensor

Hi Buy a naked read switch - like http://www.ebay.co.uk/itm/10X-Functional-Reed-Switch-10W-Low-Voltage-Current-Open-Magnetic-Switch-2x14mm-/301379307661?hash=item462b9b488d Wind several turns of solid core wire round it to form a coil - enameled wire is best - how many turns depends on the current t...
by grahamed
Sat Sep 05, 2015 3:21 pm
Forum: Automation, sensing and robotics
Topic: Multiple high-powered LEDs
Replies: 5
Views: 1379

Re: Multiple high-powered LEDs

Hi These LEDs (like all bare LEDs) require d.c. power. SSRs are generally used for a.c. only (with forced commutation you can use some SSRs on d.c.) Probably best using proper constant current LED drivers and controlling these with PWM to dim. The power requirement will be quite high so you will mos...
by grahamed
Sat Sep 05, 2015 1:07 pm
Forum: Automation, sensing and robotics
Topic: RF signal found and recorded but not picked up by Pi
Replies: 1
Views: 946

Re: RF signal found and recorded but not picked up by Pi

Hi Such questions have been asked a number of times. Try connecting Rx to 0V and 5V with a LED/R from data pin to 5V. The LED should flicker continuously and randomly. When a signal comes by the flicker turns more organised looking - it is helpful to have a remote nearby to click whilst observing LE...
by grahamed
Fri Aug 21, 2015 5:03 pm
Forum: Beginners
Topic: Unable to download Raspian
Replies: 5
Views: 724

Re: Unable to download Raspian

Hi

Thanks for the input.

16G card has rebooted 20x or so, then it failed....

So I have a faulty card.....I guess. Have just ordered an 8G NOOBS from RPF, if that fails then I guess it is the Pi2 itself.

And the download mismatch SHA1 was sent to confuse me.
by grahamed
Thu Aug 20, 2015 9:23 pm
Forum: Beginners
Topic: Unable to download Raspian
Replies: 5
Views: 724

Re: Unable to download Raspian

Downloaded again, now FCIV SHA1 agrees, and Pi2 boots (and reboots twice) on same 16G card.. Well I dunno...Chrome said download had finished. Maybe Chrome lied though filesize is same.
by grahamed
Thu Aug 20, 2015 9:06 pm
Forum: Beginners
Topic: Unable to download Raspian
Replies: 5
Views: 724

Re: Unable to download Raspian

drgeoff wrote:Sounds more like a card problem to me.
Yes it probably is the card but why is the SHA-1 being reported wrong. I have now downloaded another SHA-1 checker and that is saying the same as FCIV but not same as web page....
by grahamed
Thu Aug 20, 2015 7:19 pm
Forum: Beginners
Topic: Unable to download Raspian
Replies: 5
Views: 724

Unable to download Raspian

Hi Well this is very odd. I just can't seem to download Raspian. I have done so many times in past but no more. The download proceeds OK, I unzip and send file to 16G class 10 micro SDHD card using Windiskimager OK. But my brand new Pi2 will not boot - starts OK then multiple I/O error messages. Tri...
by grahamed
Mon May 18, 2015 8:44 pm
Forum: Automation, sensing and robotics
Topic: Raspberry Pi Switch
Replies: 4
Views: 1323

Re: Raspberry Pi Switch

Hi I commented on the circuit. The OP asked whether it would work? Obviously as intended it would work, but equally obviously as the schematic is drawn it would not. Since the OP did not seem to know the difference between N and P-channel and failed to spot the forward biased diode, and shows the 5V...
by grahamed
Sat May 16, 2015 8:42 pm
Forum: Automation, sensing and robotics
Topic: Raspberry Pi Switch
Replies: 4
Views: 1323

Re: Raspberry Pi Switch

Hi There's something wrong here.... The FET as drawn is not correct for a IRLZ34NPBF. It is a P-channel which would be happier in the 5V rail - as shown the body diode would conduct whenever the anode is positive of the cathode, i.e. all the time. An N-channel IRLZ34NPBF should switch on OK with 5V ...
by grahamed
Tue May 12, 2015 2:17 pm
Forum: Automation, sensing and robotics
Topic: photodetector for 650nm laser?
Replies: 6
Views: 3699

Re: photodetector for 650nm laser?

Hi It seems to me that you have two choices - stop the sensor seeing ambient light or make the laser light somehow different to normal light. I guess if you put a long-ish tube over the sensor so that only light from a very specific angle would pass down it the system would become quite insensitive ...
by grahamed
Wed May 06, 2015 10:13 pm
Forum: Automation, sensing and robotics
Topic: Vehicle speed and license plate monitoring
Replies: 24
Views: 13514

Re: Vehicle speed and license plate monitoring

Hi Why an ADC with the HB100? The velocity info is contained in the frequency of the FREQ_OUT signal. The 'scope view on https://www.tindie.com/products/limpkin/hb100-doppler-module-with-backpack-1/ shows a digital signal (FREQ_OUT presumably) and an analog (V_OUT presumably). A couple of resistors ...
by grahamed
Wed May 06, 2015 9:43 pm
Forum: Automation, sensing and robotics
Topic: Negative and Positive output
Replies: 2
Views: 729

Re: Negative and Positive output

Hi In the Pi context an H-bridge is normally connected and controlled so as to provide two complementary outputs each being, at any one time, either a positive supply or 0V (or both the same for no voltage across the load) The OP seems to be asking for a single output which is, at any given time, ei...
by grahamed
Sun Mar 01, 2015 11:48 am
Forum: Automation, sensing and robotics
Topic: help wiring up power relay bars
Replies: 26
Views: 2894

Re: help wiring up power relay bars

Hi True, I think the problem lay in the question. Seriously I am 100% certain that a good PSU of 2A or more would work - unless I can't do sums anymore which is likely I admit. Have you any decoupling caps on your 23107? Fitting a 100nF across the rails as near to the pins as possible is mandatory. ...
by grahamed
Sat Feb 28, 2015 8:46 pm
Forum: Automation, sensing and robotics
Topic: help wiring up power relay bars
Replies: 26
Views: 2894

Re: help wiring up power relay bars

Hi I am probably wrong. I just remember something about these pins, or maybe it was the SPI pins? But I am certainly wrong - at VDD= 5V the I2C pins of 203107 need 5V*0.8= 4V for a high, the Pi gives 3V3 so seems that the 23107 must be powered by 3V3 allowing the pull-ups on the Pi 3V3 to do their t...

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