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by davef
Thu Jan 03, 2019 11:08 pm
Forum: Networking and servers
Topic: Switching wlan0 connections takes a long time
Replies: 12
Views: 1251

Re: Switching wlan0 connections takes a long time

Hi epoch1970, Thanks for the added information. After your comments, I think the snippet I have included is not pointing to the real problem. I saw Association request to the driver failed as the likely issue, possibly an incorrect assumption. The Android AP8362 is on the dhcp managed network and co...
by davef
Wed Jan 02, 2019 6:41 pm
Forum: Networking and servers
Topic: Switching wlan0 connections takes a long time
Replies: 12
Views: 1251

Re: Switching wlan0 connections takes a long time

epoch1970, Thank you for your response. Here is a snippet of syslog Jan 2 23:59:14 raspberrypi networking[31505]: DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 17 Jan 2 23:59:16 raspberrypi wpa_supplicant[31558]: wlan0: Trying to associate with 1c:af:05:39:1a:93 (SSID='AndroidAP8362' fre...
by davef
Fri Dec 28, 2018 7:50 pm
Forum: Networking and servers
Topic: Switching wlan0 connections takes a long time
Replies: 12
Views: 1251

Switching wlan0 connections takes a long time

On a RaspPi 3 with an up to date Jessie distro. I have one network (wlan0) which the Pi uses dhcp to connect to a hotspot and on the same network (wlan0) where I use a static IP to connect to a ESP8266. As per tutorials on modifying the dhcpcd.conf file. When I switch from the dhcp managed connectio...
by davef
Fri Oct 12, 2018 4:28 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: GPIO protection circuit for oscillating input voltage
Replies: 8
Views: 2173

Re: GPIO protection circuit for oscillating input voltage

@Brandon92

Spikes I can see could be a problem with a simple voltage divider. I have used https://www.bourns.com/docs/technical-d ... t_form.pdf in the past.

Thanks for the reply.
by davef
Fri Oct 12, 2018 8:45 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: GPIO protection circuit for oscillating input voltage
Replies: 8
Views: 2173

Re: GPIO protection circuit for oscillating input voltage

Making sure that 3V3 is the maximum voltage applied to the GPIO. I understand that for isolation reasons an optocoupler is a better approach, ie especially circuits connected to mains power. But for DC and with common grounding in an installation are not voltage dividers or level shifters more appro...
by davef
Tue Apr 17, 2018 1:27 am
Forum: Automation, sensing and robotics
Topic: Monitoring a 12v solar & battery system
Replies: 10
Views: 12146

Re: Monitoring a 12v solar & battery system

Lorcan, Regarding the LTC6104 send me a private message. I think HM is a high voltage version, which I use for my 26V house bank system. You won't need that variant. Well, the shunt does consume some power as there is a voltage drop across it. The Hall effect module also. I would have to crunch the ...
by davef
Sun Apr 15, 2018 10:47 pm
Forum: Automation, sensing and robotics
Topic: Monitoring a 12v solar & battery system
Replies: 10
Views: 12146

Re: Monitoring a 12v solar & battery system

A shunt is a common method. I use one in the positive lead of the battery to inverter lead. This requires a hi-side current sense chip (LTC1601). It has a DC amplifier built into it so feeding this off to a 8bit ADC would be adequate. Just FYI, I see those most UK caravan modifications seem to sugge...
by davef
Sun Apr 15, 2018 10:34 pm
Forum: Automation, sensing and robotics
Topic: Long-Range RPI communication with mobile device
Replies: 16
Views: 2678

Re: Long-Range RPI communication with mobile device

I will second LORA.

I am starting a project based on this work:
http://cpham.perso.univ-pau.fr/LORA/RPIgateway.html

Excellent work and very comprehensive.

Good luck!
by davef
Sun Apr 15, 2018 10:41 am
Forum: Automation, sensing and robotics
Topic: Long-Range RPI communication with mobile device
Replies: 16
Views: 2678

Re: Long-Range RPI communication with mobile device

Think there is a bit of an issue here. Sending 1MB of data and trying to get a response within 0.1 to 1 second, I think is a tall order. Even 1Mb. By response, I mean time taken to start sending the waypoint information until you want the drone to change course. Less that 1MB per file approx 800kb. ...
by davef
Sat Apr 14, 2018 11:02 am
Forum: Automation, sensing and robotics
Topic: Long-Range RPI communication with mobile device
Replies: 16
Views: 2678

Re: Long-Range RPI communication with mobile device

Don't think a cloud service is going to be anywhere that quick. I would have a closer look at how fast a cellular modem setup would respond.

How much data is involved in each update and how often could the updates happen?
by davef
Thu Apr 12, 2018 7:49 am
Forum: Automation, sensing and robotics
Topic: Long-Range RPI communication with mobile device
Replies: 16
Views: 2678

Re: Long-Range RPI communication with mobile device

Quite quick might not be fast enough. 10 seconds, 1 sec. 0.1 seconds. Maybe a cellular connection, maybe a Cloud service like Hologram, etc.
by davef
Sat Apr 07, 2018 7:31 pm
Forum: Automation, sensing and robotics
Topic: Long-Range RPI communication with mobile device
Replies: 16
Views: 2678

Re: Long-Range RPI communication with mobile device

You need to give some idea of the latency (time to respond to commands) that you would like in your system.
by davef
Sat Apr 07, 2018 10:29 am
Forum: Advanced users
Topic: Raspberry 3+ wifi antenna
Replies: 33
Views: 31341

Re: Raspberry 3+ wifi antenna

Had a look at the above viewtopic. Strictly, speaking if they were using the spec an to sample the signal they would have to use an in-line directional coupler or an RF splitter. Slapping the another 50 Ohm load (the spec an) at this position to going to place an non-50 Ohm load on the WiFi chip and...
by davef
Fri Mar 16, 2018 7:26 pm
Forum: General discussion
Topic: Running a bash script via PHP
Replies: 4
Views: 4799

Re: Running a bash script via PHP

Several things I would check out: 1) I noticed you are using sh instead of bash for one of the scripts. There was some recent discussion on that. 2) In my PHP scripts I have !#/bin/php5 before the <?php I haven't tried leaving it since I got them to work! 3) chmod 755 4) maybe you need to look at ch...
by davef
Mon Mar 05, 2018 7:35 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Modifying 10-bit c++ SPI code for a 12-bit device
Replies: 6
Views: 1774

Re: Modifying 10-bit c++ SPI code for a 12-bit device

I see no one else has answered so I'll have a crack at it :) 0b tells you that it binary notation not a hex or decimal representation. <<4 and <<8 could be just doing something with bit 4 or bit 8. For the AVR 8bit uPs it is an idiom to perform some math function on the value, maybe Google will help...
by davef
Tue Feb 27, 2018 11:30 pm
Forum: Automation, sensing and robotics
Topic: How to turn on and off a raspberry pi every day for some minute?
Replies: 9
Views: 2925

Re: How to turn on and off a raspberry pi every day for some minute?

Had a quick look at your links. The last one is the only one that specifies a standby or self-consumption current. 20mA. That is probably going to hurt your battery lifetime. An 8bit uP with power-down and power-save modes ie the ATmega88P/PV series to turn the PI on is going to be much easier on th...
by davef
Mon Feb 19, 2018 9:43 am
Forum: Automation, sensing and robotics
Topic: Temperature trending with DS18b20
Replies: 6
Views: 1483

Re: Temperature trending with DS18b20

Don't know about the best way, but would "moving average" help? Due to the complexity of the system maybe you need several sensors, ie one in the circulation system.

You might find some hits on "hot water tank stratification".
by davef
Tue Feb 06, 2018 6:15 pm
Forum: Beginners
Topic: i2c or spi?
Replies: 12
Views: 2304

Re: i2c or spi?

Your assumptions are correct, but looking at the picture I see a CS pin, which is normally associated with SPI. Another image comes up showing a part which says IIC in the description and has fewer pins. There could be many other reasons why you don't get the correct response to i2cdetect. Datasheet...
by davef
Sun Jan 28, 2018 10:03 am
Forum: Automation, sensing and robotics
Topic: Powering on the PI whith a MOSFET
Replies: 1
Views: 432

Re: Powering on the PI whith a MOSFET

Try searching for "hi-side MOSFET switch P channel".
by davef
Thu Jan 11, 2018 8:36 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: 1-wire DS18B20 disappears
Replies: 54
Views: 15291

Re: 1-wire DS18B20 disappears

@rickrack,

Could you post a link to these hints? For the last year I have had to ignore 0C readings in my datalogger.

It would be nice to know what is going wrong.

davef
by davef
Wed Dec 27, 2017 5:36 am
Forum: Automation, sensing and robotics
Topic: 24V to 5V DC to DC conversion
Replies: 21
Views: 22914

Re: 24V to 5V DC to DC conversion

The RPi further regulates the 5v input down to a 3.3v so the 5v input isn't that critical as long as the it is within the 3.3v regulator specs.
I believe that you want to be within the recommended voltages for USB devices ... as well.
by davef
Fri Dec 15, 2017 12:17 am
Forum: Automation, sensing and robotics
Topic: 433MHz problems for both remote control sockets and pir respectively
Replies: 6
Views: 1534

Re: 433MHz problems

Just a suggestion ... you attracted me because I am an RF guy but your problem has nothing to do with RF ... so try to come up with a more descriptive title.

Maybe the control signals are specific to your product or to PIR sensors in general.
by davef
Wed Nov 15, 2017 11:58 pm
Forum: Automation, sensing and robotics
Topic: Raspberry and Arduino RF Communication range problem with rc-switch
Replies: 12
Views: 3555

Re: Raspberry and Arduino RF Communication range problem with rc-switch

Preamble is a keyword that will help your searching.
by davef
Tue Aug 15, 2017 7:36 pm
Forum: Automation, sensing and robotics
Topic: HELP NEEDED - Remotely control lights with RF transmitter
Replies: 3
Views: 2249

Re: HELP NEEDED - Remotely control lights with RF transmitter

It might be easier to work out what current and voltages the push buttons are controlling and interface the Pi's GPIO to the wireless board.

Chip data:
http://chiprui.com/productshow.asp?id=5 ... roduct.asp
by davef
Mon Apr 24, 2017 10:16 pm
Forum: Off topic discussion
Topic: wifi signal in wavemon raspberry pi
Replies: 5
Views: 1709

Re: wifi signal in wavemon raspberry pi

Show the links to a positive dBm signal level. RSSI is a positive number. You can map a range of negative dBm signal levels to a representative positive RSSI reading. If you use the same dongle in both situations and they are in the exact same physical location and nothing has changed in the environ...

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