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by stevend
Tue Oct 27, 2020 9:59 pm
Forum: Automation, sensing and robotics
Topic: Sensing Location Ball is Thrown
Replies: 6
Views: 182

Re: Sensing Location Ball is Thrown

Lbox1 wrote:
Tue Oct 27, 2020 9:37 pm
stick a magnet in/on the ball and use hall effect sensors in the cup to detect the magnetic field.
You could use a reed switch - fast operation and simple to interface - just a switch input to a Pi.
by stevend
Sun Oct 25, 2020 7:36 pm
Forum: General discussion
Topic: Writing a new library that uses I2C channels
Replies: 12
Views: 432

Re: Writing a new library that uses I2C channels

It is MCP4728 chip. In page 33 of the manual you can see that you have to change the third line before ACK. This is only for "GENERAL CALL READ ADDRESS BITS". Timing is much less critical when actually using the DACs (and you don't have to use the /LDAC line at all). Do you actually need the Genera...
by stevend
Sat Oct 17, 2020 6:46 pm
Forum: General discussion
Topic: Accessing EEPROM memory from file system
Replies: 13
Views: 417

Re: Accessing EEPROM memory from file system

Okay questions, How are you accessing the F-RAM with a program or kernel driver? What F-RAM chip are you using? And would your setup work for the OP? I've actually been using FRAM on embedded non-Linux systems; hence my vagueness on some points. Similarly with LittleFS; however I do know that the p...
by stevend
Sat Oct 17, 2020 8:22 am
Forum: General discussion
Topic: Accessing EEPROM memory from file system
Replies: 13
Views: 417

Re: Accessing EEPROM memory from file system

I'd be interested in F-RAM for my kiosk project it's nice having a little non-volitial memory but more would be welcome. I'm interested in how this all unfolds I've been using I2C FRAM for years, and found it rock solid and very simple to use - byte-sized access for both read and write, and no need...
by stevend
Fri Oct 16, 2020 8:11 pm
Forum: General discussion
Topic: Accessing EEPROM memory from file system
Replies: 13
Views: 417

Re: Accessing EEPROM memory from file system

I agree though using an eeprom like this isn't really a good idea when the goal is to the SD card an eeprom will not hold much data. The fram on the other hand wouldn't ware out and would make for an interesting proof of concept. Again the space is going to be minimal and not useful for logs Depend...
by stevend
Fri Oct 16, 2020 1:19 pm
Forum: General discussion
Topic: Accessing EEPROM memory from file system
Replies: 13
Views: 417

Re: Accessing EEPROM memory from file system

I'm assuming you want to attach an EEPROM or FRAM chip to your Pi, and use that for storage. FRAM is slightly easier to code for, but costs more. It will probably be an 8-pin chip with a serial-type interface; if so, go for SPI rather than I2C (faster). You could look at littleFS , which is designed...
by stevend
Tue Sep 08, 2020 5:01 pm
Forum: Automation, sensing and robotics
Topic: LSIS PLC to PI communications
Replies: 14
Views: 568

Re: LSIS PLC to PI communications

Modbus started life as a serial protocol; Ethernet came later. So AFAIK serial is your only option. For best noise immunity and transmission distance I'd go with RS-485; make sure you use termination resistors, at least at the receive ends. If you're in a noisy environment consider electrically isol...
by stevend
Mon Sep 07, 2020 12:23 pm
Forum: Automation, sensing and robotics
Topic: Motor Driver Board should stop motor when torque > limit
Replies: 4
Views: 319

Re: Motor Driver Board should stop motor when torque > limit

As a safety feature, you could measure the time taken for end to end travel, increase it by (say) 10%, and always turn off the drive after this time if none of the other termination conditions have been met. The encoder already suggested can use either a magnet and hall effect sensor, or a slotted o...
by stevend
Tue Sep 01, 2020 11:55 am
Forum: General discussion
Topic: Would you buy time on a RasPi satellite?
Replies: 20
Views: 866

Re: Would you buy time on a RasPi satellite?

Today, if you want to play around with a satellite, you basically need to be a satellite operator. Not necessarily; depends what you want to do with the satellite, but certainly for data transmission you can rent time by the hour (often used by news organisations for outside broadcasts - people may...
by stevend
Thu Aug 20, 2020 1:22 pm
Forum: Automation, sensing and robotics
Topic: External power supply for relay and IO extpansion
Replies: 4
Views: 344

Re: External power supply for relay and IO extpansion

I wonder if I power all elements from single 5V Power Supply, it would solve a problem? Depends what problem you're trying to solve! The RPi I2C signals operate at 3.3V, so you will need a level shifter anyway. The Si8600 conveniently does this; you power the Pi side from 3.3V, and the I/O side fro...
by stevend
Wed Aug 19, 2020 5:24 pm
Forum: Automation, sensing and robotics
Topic: External power supply for relay and IO extpansion
Replies: 4
Views: 344

Re: External power supply for relay and IO extpansion

Use a device such as the Si8600 to isolate the I2C bus electrically. Note: On the Si8600 it can matter which side is which; try before making anything permanent.

Then have two separate power supplies; one for the Pi, and one for all the I/O.
by stevend
Tue Aug 18, 2020 12:23 pm
Forum: Other projects
Topic: Advice / feasibility of borehole inspection idea
Replies: 10
Views: 612

Re: Advice / feasibility of borehole inspection idea

I like the idea of the optical fibre connection to tackle this distance issue, however it doesn’t seem RPI with fiber optic connection is particularly well established..? Are there any examples of communicating video between two RPI using fiber? You're unlikely to find Pi-specific fibre based solut...
by stevend
Mon Aug 17, 2020 5:00 pm
Forum: Other projects
Topic: Advice / feasibility of borehole inspection idea
Replies: 10
Views: 612

Re: Advice / feasibility of borehole inspection idea

For power, feed a relatively high voltage (50V say) in at the top, then convert to whatever you need at the business end using an efficient dc-dc converter (i.e. probably not eBay's finest). 'Proper' power over Ethernet works this way. This reduces the current down the cable, reducing voltage drop p...
by stevend
Wed Aug 12, 2020 12:36 pm
Forum: Automation, sensing and robotics
Topic: Using LM358 Op Amp to step up clock output from gpio
Replies: 13
Views: 740

Re: Using LM358 Op Amp to step up clock output from gpio

Also, in the second diagram R1 is too high a value, and if the 24V supply is of reasonable quality, could be replaced by a link. The LM358 is going to take some current all the time, which is going to reduce its supply voltage due to voltage drop across R1. Then when the LED turns on that will take ...
by stevend
Wed Aug 05, 2020 12:39 pm
Forum: Automation, sensing and robotics
Topic: Stepper Motor Freaks Out When Relay Turns On Pump
Replies: 2
Views: 184

Re: Stepper Motor Freaks Out When Relay Turns On Pump

Have you got high-frequency decoupling capacitors in strategic places? Something in the region of 10nF to 100nF ceramic. Typical places would be across the pump motor coils, and across the supply in the area that does the switches. It's also possible that the stepper driver doesn't have enough decou...
by stevend
Mon Jul 27, 2020 4:06 pm
Forum: General discussion
Topic: 7 Inch LCD causing PI reset
Replies: 3
Views: 195

Re: 7 Inch LCD causing PI reset

Sounds as if it could be a power supply being overloaded. How are you powering the setup?
by stevend
Fri Jul 24, 2020 8:48 pm
Forum: General discussion
Topic: Windows on ARM
Replies: 36
Views: 1495

Re: Windows on ARM

It's not that some Linux alternatives aren't available, but all of these programs whether Windows or Linux are moderately complex and fairly different from one another. One powerful Linux program called weewx is going to be beyond the capabilities of many such hobbyists to set up. I've just looked ...
by stevend
Wed Jul 22, 2020 12:33 pm
Forum: General discussion
Topic: Raspberry Pi Posts 'necro posting'
Replies: 35
Views: 1464

Re: Raspberry Pi Posts 'necro posting'

Rather than lock threads, would it be possible to simply bring up a warning message when the user hits 'Reply' on an old thread? With the option to cancel or continue.
The warning message could encapsulate some of the issues raised in this thread about possibly outdated information and so on.
by stevend
Fri Jul 17, 2020 4:59 pm
Forum: Off topic discussion
Topic: Modelling irregular shapes in 3D CAD
Replies: 4
Views: 654

Re: Modelling irregular shapes in 3D CAD

Assuming a 2D drawing is a useful start, how about the following: Tape a coloured background behind the frame; choose the colour to give a good contrast so the edge stands out. Tape a ruler somewhere. Take a high resolution photo. Scale the photo to be 1:1 (or maybe after the next step). Use the cur...
by stevend
Wed Jul 15, 2020 12:46 pm
Forum: Automation, sensing and robotics
Topic: Connect RPi to Texecom Alarm Panel Digicom Outputs
Replies: 4
Views: 369

Re: Connect RPi to Texecom Alarm Panel Digicom Outputs

pcmanbob wrote:
Wed Jul 15, 2020 9:35 am
It sounds like they may be open collector outputs, I would suggest testing them with multimeter set on volts DC as your first job.
They are indeed open collector outputs; ULN2803 IIRC
by stevend
Wed Jul 08, 2020 12:22 pm
Forum: Automation, sensing and robotics
Topic: VL53L0X 'crashes' I2C Bus 1. What gives?
Replies: 5
Views: 325

Re: VL53L0X 'crashes' I2C Bus 1. What gives?

You need to be very sure that the Pi's pins don't go above 3.3V, so any pullups on the I2C bus must go to 3.3V, never 5V. Do you have a schematic for the breakout board, to check how its connected? Not sure how i2cdetect detects devices, so maybe it doesn't work with the VL53L0X - maybe someone who'...
by stevend
Tue Jul 07, 2020 7:45 pm
Forum: Other projects
Topic: Advice on Sensor Wire lengths
Replies: 9
Views: 487

Re: Advice on Sensor Wire lengths

Final thing to throw into the mix is point to point low power radio links; these are simpler (and, I suspect, draw rather less power) than WiFi based solutions, and if you get the right setup they are designed for the distance you need to cover, rather than adapting WiFi in a way it perhaps wasn't r...
by stevend
Tue Jul 07, 2020 7:30 pm
Forum: Automation, sensing and robotics
Topic: VL53L0X 'crashes' I2C Bus 1. What gives?
Replies: 5
Views: 325

Re: VL53L0X 'crashes' I2C Bus 1. What gives?

According to that link, the sensor will run off 3-5V power. So as a first step, power the board from 3.3V rather than 5V. It's remotely possible that the board has pullup resistors on the I2C bus - you're unlikely to have damaged the Pi if it has, but it might have confused things. If you have no pu...
by stevend
Tue Jul 07, 2020 12:32 pm
Forum: General discussion
Topic: Recharable battry for DS3231
Replies: 8
Views: 408

Re: Recharable battry for DS3231

I agree with comments about avoiding rechargeable batteries, since they are often the least reliable part of the circuit, although probably better than when I had a board running for 20-25 years without failure, other than replacing the NiCad rechargeable every five years or so. I also try and avoid...
by stevend
Tue Jul 07, 2020 12:25 pm
Forum: Other projects
Topic: Advice on Sensor Wire lengths
Replies: 9
Views: 487

Re: Advice on Sensor Wire lengths

That's essentially an analog sensor, so at risk of interference, and cable length will add resistance; net result, uncertainty in the readings. Personally I wouldn't even think about putting an analog sensor on the end of that length of wire unless there was absolutely no other solution. I suggest a...

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