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by techpaul
Sun Mar 16, 2014 1:33 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Analog signal to DAC
Replies: 16
Views: 2943

Re: Analog signal to DAC

Here is some annotated circuit symbols for an 8 bit DAC and 8 bit ADC, I believe still available and datasheets exist for TDA8702 and TDA8703

Please explain on which pins you would connect the analog signal as an INPUT on the DAC what levels, type and frequency it would be
by techpaul
Sun Mar 16, 2014 1:16 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Analog signal to DAC
Replies: 16
Views: 2943

Re: Analog signal to DAC

DTM450 wrote:Image

ok this is probably the only way i can explain it, what are the resulting signal outputs from these inputs
The top diagram makes no sense as it is back to front and shows an IN that is an OUT
by techpaul
Sun Mar 16, 2014 12:00 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Analog signal to DAC
Replies: 16
Views: 2943

Re: Analog signal to DAC

Putting an signal INTO a DAC does NOT get a digital output, you may well BLOW the DAC. These devices DAC and ADC are ONE direction devices, you cannot change the direction. Just like you would not expect connecting microphone to headphone/speaker output to chnage the output into an input to an audio...
by techpaul
Sun Mar 16, 2014 11:54 am
Forum: Python
Topic: Bit banging to read/write RDS info
Replies: 141
Views: 17407

Re: Bit banging to read/write RDS info

Just spotted you are using ord() function the question is why? This is only useful for Unicde/ASCii conversions, just sending 'H' will send ASCII (8bit value) not potentially a 16bit Unicode value.
by techpaul
Sun Mar 16, 2014 11:48 am
Forum: Python
Topic: Bit banging to read/write RDS info
Replies: 141
Views: 17407

Re: Bit banging to read/write RDS info

I suggest that you have not connected the I2C correctly and added pullup resistors when you should not or powered device wrong or similar can we see your actual circuit diagram. When using I2C addresses use actual address to smbus do NOT shift them left or right pass the 7 bit address as is. Proabbl...
by techpaul
Sun Mar 16, 2014 11:35 am
Forum: Python
Topic: Binary Counter without using shift register such as 74HC595
Replies: 4
Views: 2290

Re: Binary Counter without using shift register such as 74HC

Better code would setup the pins as outputs ONCE in main (or a function called from main.

Also not use a complicated

Code: Select all

light((m * j) / m)
line just call the light function then use BINARY AND function to scan over the value and mask which bit to determine action, moving mask with >> or << operations.
by techpaul
Sun Mar 16, 2014 11:25 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Analog signal to DAC
Replies: 16
Views: 2943

Re: Analog signal to DAC

Best you describe what you mean and which way signals are flowing to which parts of a DAC or ADC, as what you are saying does not make sense. DAC have OUTPUTs of analog signals, it is rare for analog signals to go IN a DAC, no analog signals go through a DAC or ADC. In some cases an analog signal i...
by techpaul
Sun Mar 16, 2014 11:21 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Analog signal to DAC
Replies: 16
Views: 2943

Re: Analog signal to DAC

Best you describe what you mean and which way signals are flowing to which parts of a DAC or ADC, as what you are saying does not make sense. DAC have OUTPUTs of analog signals, it is rare for analog signals to go IN a DAC, no analog signals go through a DAC or ADC. In some cases an analog signal is...
by techpaul
Sat Mar 15, 2014 12:28 am
Forum: Automation, sensing and robotics
Topic: Driving a DC to DC SSR for Solenoid Valve-Voltage leak issue
Replies: 24
Views: 4123

Re: Driving a DC to DC SSR for Solenoid Valve-Voltage leak i

There appears to be things missing in photo.

Can you post a simple circuit diagram of what you ar doing and manufacturers part number of SSR or datasheet link.
by techpaul
Sat Mar 15, 2014 12:23 am
Forum: Other projects
Topic: Pi in high magnetic fields
Replies: 42
Views: 8556

Re: Pi in high magnetic fields

aTao wrote:Mirrors and zoom lenses dont suffer from magnetic fields.
The 'silver' backing might actually, if you can find a non metallic mirror you might do better.
by techpaul
Fri Mar 14, 2014 7:06 pm
Forum: Other projects
Topic: Pi in high magnetic fields
Replies: 42
Views: 8556

Re: Pi in high magnetic fields

If *I* wanted to do this, I would: - NOT have the Pi tethered with USB/Ethernet - put the Pi in a Faraday cage to minimize potential RF interference (may not be needed) Beware of faraday cage becoming a one turn secondary and causing other problems... In this size of field having an air core transf...
by techpaul
Fri Mar 14, 2014 6:16 pm
Forum: Other projects
Topic: Pi in high magnetic fields
Replies: 42
Views: 8556

Re: Pi in high magnetic fields

Trouble with endoscopes is the fireld of view or if you have field of view lack of resolution. Let alone lighting issues and other losses.

Been involved with many types of endoscopes, even medical grade 3D endocscopes
by techpaul
Fri Mar 14, 2014 4:33 pm
Forum: Other projects
Topic: Pi in high magnetic fields
Replies: 42
Views: 8556

Re: Pi in high magnetic fields

Personally in this situation I would use some form of standard camera with analog output and good lens to zoom to area of interest. Then get a video to fibre optic converter run the video feed as a fibre optic out of the room convert back to analog outside the room then work on how to distribute/str...
by techpaul
Fri Mar 14, 2014 4:21 pm
Forum: Other projects
Topic: Pi in high magnetic fields
Replies: 42
Views: 8556

Re: Pi in high magnetic fields

A USB-Ethernet device seems workable. A standard passive USB cable can be 3 meters long, The spec has always been 5m passive cable and any USB devices/hubs I have ever designed have always been tested with 5m passive cables as worst case scenario and much longer with an active cable (which has one ...
by techpaul
Fri Mar 14, 2014 4:15 pm
Forum: Other projects
Topic: Pi in high magnetic fields
Replies: 42
Views: 8556

Re: Pi in high magnetic fields

In such a strong magnetic field be careful how you screen, as your screening can become the secondary of an air gapped transformer with a one turn secondary. It is for this reason that electricians have to be careful on how they route wires in such rooms for mains wiring, and MUST have a slot in any...
by techpaul
Thu Mar 13, 2014 10:40 pm
Forum: Automation, sensing and robotics
Topic: MCP23017 Registers
Replies: 2
Views: 814

Re: MCP23017 Registers

Hello, I am experimenting with an MCP23017, but I would greatly appreciate some clarification on using GPA/B pins as inputs. I have set GPA7 as an input and GPA1-6 as outputs using: i2cset -y 1 0×20 0×00 0×80. When I hold GPA7 at either 0v or 3.3v, I was expecting to read the GPIOA register using: ...
by techpaul
Mon Mar 10, 2014 10:06 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Raspberry Pi PIR motion sensor with Schmitt Trigger
Replies: 3
Views: 2345

Re: Raspberry Pi PIR motion sensor with Schmitt Trigger

Thank you for your reply to my post. The PIR I have in my hand is a very low cost one which is not much specified: http://www.dealextreme.com/p/ir-infrared-motion-detector-sensor-module-dc-5v-20v-122286?item=28 But is seems like this device is also already Schmitt triggered for 20ms. But I wonder h...
by techpaul
Fri Mar 07, 2014 2:33 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Raspberry Pi PIR motion sensor with Schmitt Trigger
Replies: 3
Views: 2345

Re: Raspberry Pi PIR motion sensor with Schmitt Trigger

First look at what your PIR detectors can do there is a range made by Panasonic that do most of your work for you they come in 2 ranges 5V (Vcc=3 to 6V) standby current typically 170uA 3V (Vcc=2 to 3V) standby current typically 50uA The output pulse is ALREADY schmitt triggered and lasts at least 10...
by techpaul
Wed Mar 05, 2014 4:58 pm
Forum: C/C++
Topic: Using C and GPIO to get monitor RPMs
Replies: 7
Views: 5169

Re: Using C and GPIO to get monitor RPMs

Hello, I'm new to the Rpi and greatly need some help. I'm attempting to connect an open collector type sensor to an input on the gpio header. I'm using it with a type of encoder wheel attached to a DC motor. I need my C program to get a pulse rate/sec. on that input and present a value that can be ...
by techpaul
Wed Mar 05, 2014 4:39 pm
Forum: General discussion
Topic: Quick P.I.R. advice
Replies: 9
Views: 1369

Re: Quick P.I.R. advice

So your current BCM pins of 23 and 24 map to the BOARD pins of 16 and 18 respectively, and its these numbers you must use in your code (or change GPIO.setmode(GPIO.BCM)) NO if using setmode(GPIO.board) you must use MATCHING numbers, so if using connector pins 23 and 24 and BOARD numbering, then sof...
by techpaul
Wed Mar 05, 2014 1:22 pm
Forum: General discussion
Topic: Quick P.I.R. advice
Replies: 9
Views: 1369

Re: Quick P.I.R. advice

Hi TechPaul, many thanks for your response, i didnt realise Python was so picky with indentation....too used to my day to day of VB.net stuff. Sometimes people refer to Python as a tab[indentation] nazi for its block structure relying on the same whitespace for each indent level anyway back on topi...
by techpaul
Tue Mar 04, 2014 8:59 am
Forum: General discussion
Topic: Quick P.I.R. advice
Replies: 9
Views: 1369

Re: Quick P.I.R. advice

Other than seeing some indentation problems what is your problem? Minor tweaks to indents as Python is VERY picking on exact indent spacing matching # Import required Python libraries import RPi.GPIO as GPIO import time # Use BOARD GPIO references # instead of physical pin numbers GPIO.setmode(GPIO....
by techpaul
Tue Mar 04, 2014 8:36 am
Forum: Beginners
Topic: Supplying a clock for an ADC ic
Replies: 49
Views: 8487

Re: Supplying a clock for an ADC ic

What you need to do is use pencil and paper about your 'whole' system and how data and calculations are done at each stage.These are calculations about data flow and loading you need to do we do not need to see the workings What is min and max duration of whole process Is this continuous for mins, h...
by techpaul
Mon Mar 03, 2014 5:31 pm
Forum: Beginners
Topic: Supplying a clock for an ADC ic
Replies: 49
Views: 8487

Re: Supplying a clock for an ADC ic

As it would seem that performing sampling on the Pi would not be practical in my case due to its CPU intensiveness (considering I also will need to perform signal analysis with FFT implementation), an additional auxiliary device to process the samples would be needed. For example, what if I were to...
by techpaul
Mon Mar 03, 2014 2:13 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Where to get mission control style buttons?
Replies: 5
Views: 1050

Re: Where to get mission control style buttons?

Fairly standard range of industrial grade switches look at most distributors or manufacturers like Omron, ITT, ITW and their websites then find who distributes them.

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