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by tdenson
Tue May 30, 2017 10:16 am
Forum: Automation, sensing and robotics
Topic: Mains relays that can be driven from the Pi
Replies: 27
Views: 4961

Re: Mains relays that can be driven from the Pi

Moe wrote:OK, so why do you think a relay rated at 250V /10A can't handle mains?
I never said that. It was the combination of mains/normally closed contacts/3.3V input that I couldn't find, but have now sourced
by tdenson
Mon May 29, 2017 4:24 pm
Forum: Automation, sensing and robotics
Topic: Mains relays that can be driven from the Pi
Replies: 27
Views: 4961

Re: Mains relays that can be driven from the Pi

I have no problem when I want to switch low voltages, there are ready made modules with multiple relays on the board, each with 3 output connections supporting normally open and normally closed. However, my problem came when I tried to find the same functionality but switching mains. Maybe you coul...
by tdenson
Sun May 28, 2017 6:12 pm
Forum: Automation, sensing and robotics
Topic: Mains relays that can be driven from the Pi
Replies: 27
Views: 4961

Re: Mains relays that can be driven from the Pi

pcmanbob wrote:Hi.


it seems that what you really wanted was a relay with a normally closed contact so that when the relay was off the power would be connected to your equipment.. and you switched the relay on to switch the equipment off
.
Yes
by tdenson
Sun May 28, 2017 4:12 pm
Forum: Automation, sensing and robotics
Topic: Mains relays that can be driven from the Pi
Replies: 27
Views: 4961

Re: Mains relays that can be driven from the Pi

I never asked about a latching relay, all I ever wanted was a relay which switches on/off when you apply a 3V input (from Pi) and switches off/on when you take it back to GND. Seems very simple, that's the basic function of a relay - current through a coil causes the contacts to switch. In fact I'd ...
by tdenson
Wed May 24, 2017 9:54 pm
Forum: Automation, sensing and robotics
Topic: IC for driving LEDs
Replies: 6
Views: 1028

Re: IC for driving LEDs

If you just want simple on/off control but need to drive LEDs that require more than the Pi can supply, you could look at something like the ULN2803A, it is a darlington pair array which contains 8 pairs of transistors.Its capable of driving up to 50V and 500mA. There are obviously similar packages...
by tdenson
Wed May 24, 2017 12:21 pm
Forum: Automation, sensing and robotics
Topic: IC for driving LEDs
Replies: 6
Views: 1028

Re: IC for driving LEDs

joan wrote:Have a look at the PCA9685. It is an I2C device and provides 16 channels.

It usually comes bundled in a convenient module, generally marketed as a servo driver but it's intended usage is as a PWM LED driver.

E.g. have a look on eBay for PCA9685 and PWM.
Thanks, but more sophisticated than I need
by tdenson
Wed May 24, 2017 12:20 pm
Forum: Automation, sensing and robotics
Topic: IC for driving LEDs
Replies: 6
Views: 1028

Re: IC for driving LEDs

If you just want simple on/off control but need to drive LEDs that require more than the Pi can supply, you could look at something like the ULN2803A, it is a darlington pair array which contains 8 pairs of transistors.Its capable of driving up to 50V and 500mA. There are obviously similar packages...
by tdenson
Wed May 24, 2017 8:21 am
Forum: Automation, sensing and robotics
Topic: IC for driving LEDs
Replies: 6
Views: 1028

IC for driving LEDs

I want to drive 6 LEDs from GPIO pins for a project of mine. Obviously I can wire up the LEDs with 6 transistors and resistors, but I thought there would be an IC that does the job for me. However, I have searched all the usual sources (Farnell, RS, eBay etc) in vain. It seems a simple enough requir...
by tdenson
Tue May 23, 2017 12:30 pm
Forum: Automation, sensing and robotics
Topic: Mains relays that can be driven from the Pi
Replies: 27
Views: 4961

Re: Mains relays that can be driven from the Pi

That's what I don't understand; the 'cheap' one will do 'mains' at up to 10A on its own. I use a cheap one in series with an automotive one because I need to switch a 24V 60A supply, but you don't have that problem ... unless you're switching more than 10A per relay? By "the cheap one" do you mean ...
by tdenson
Mon May 22, 2017 8:01 am
Forum: Automation, sensing and robotics
Topic: Mains relays that can be driven from the Pi
Replies: 27
Views: 4961

Re: Mains relays that can be driven from the Pi

What an odd thread. Mains relays driven by latching relays, that aren't actually latching but will easily handle mains..... Just use a damned relay. It's not rocket surgery. That's what I thought when I started this thread, it's just a relay :) However, my proposed solution of putting two relays in...
by tdenson
Sat May 20, 2017 8:31 am
Forum: Automation, sensing and robotics
Topic: Mains relays that can be driven from the Pi
Replies: 27
Views: 4961

Re: Mains relays that can be driven from the Pi

BTW you may need an RC snubber on the circuit. I had a huge issue with EMI causing my arduino and PI to reset every time the relay with a 1 amp load was flipped off. I've used these relays for a few years now and never seen any spurious triggering.It's all fairly low power stuff. What I do with the...
by tdenson
Fri May 19, 2017 7:22 am
Forum: Automation, sensing and robotics
Topic: Mains relays that can be driven from the Pi
Replies: 27
Views: 4961

Re: Mains relays that can be driven from the Pi

I would be interested in seeing the link you were you purchased these ready made pcbs with latching relays. The two below - https://www.amazon.co.uk/gp/product/B01MA1HESV/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 https://www.amazon.co.uk/gp/product/B01BWX6B9M/ref=oh_aui_search_detailpage?ie=UTF8&p...
by tdenson
Thu May 18, 2017 10:48 pm
Forum: Automation, sensing and robotics
Topic: Mains relays that can be driven from the Pi
Replies: 27
Views: 4961

Re: Mains relays that can be driven from the Pi

I would be interested in seeing the link you were you purchased these ready made pcbs with latching relays. The two below - https://www.amazon.co.uk/gp/product/B01MA1HESV/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 https://www.amazon.co.uk/gp/product/B01BWX6B9M/ref=oh_aui_search_detailpage?ie=UTF8&p...
by tdenson
Wed May 17, 2017 11:06 pm
Forum: Automation, sensing and robotics
Topic: Mains relays that can be driven from the Pi
Replies: 27
Views: 4961

Re: Mains relays that can be driven from the Pi

Hi. What you are looking for is a latching relay I think that's what I said in my OP. I have decided for the time being to drive a non-latching relay from a low voltage latching relay. Bit clunky but will do the job. You asked for a source, and I explained you would not find a ready made card and p...
by tdenson
Wed May 17, 2017 6:33 pm
Forum: Automation, sensing and robotics
Topic: Mains relays that can be driven from the Pi
Replies: 27
Views: 4961

Re: Mains relays that can be driven from the Pi

pcmanbob wrote:Hi.

What you are looking for is a latching relay
I think that's what I said in my OP.
I have decided for the time being to drive a non-latching relay from a low voltage latching relay. Bit clunky but will do the job.
by tdenson
Wed May 17, 2017 2:17 pm
Forum: Automation, sensing and robotics
Topic: Mains relays that can be driven from the Pi
Replies: 27
Views: 4961

Mains relays that can be driven from the Pi

I currently make use of low voltage relays (the Songle ones that come mounted 2/4/8 to a board) that can be triggered from GPIO pins. However, I want to use mains relays and the only ones I can find that can be driven from the Pi are what I believe are known as non-latching i.e. when you remove powe...
by tdenson
Thu Apr 20, 2017 9:17 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Connecting to the GPIO pins
Replies: 3
Views: 527

Re: Connecting to the GPIO pins

Actually, I've come up with a novel but rather radical solution. The GPIO pins that are blocking the end of the plug are not needed so I have cut them off and now I can use standard IDC connectors.
by tdenson
Wed Apr 19, 2017 11:11 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Connecting to the GPIO pins
Replies: 3
Views: 527

Connecting to the GPIO pins

I want to use only some of the GPIO pins and would like to use a ribbon cable that only has 12 connections in 2 rows of 6. However, is it possible to find ribbon cables that allow plugging in to only part of the GPIO pin header. The only ones I have will not plug in because of solid plastic at the e...
by tdenson
Tue Feb 28, 2017 9:52 pm
Forum: Media centres
Topic: Kodi on Jessie
Replies: 2
Views: 839

Re: Kodi on Jessie

barreinhard wrote:are you typing `kodi` or `Kodi`?
I simply wrote Kodi in my post because it is a name. I appreciate that the command is case sensitive.

I worked out what my problem was. I was accessing the Pi headless (via BNC). All was well when I connected a monitor.
by tdenson
Tue Feb 28, 2017 2:43 pm
Forum: Media centres
Topic: Kodi on Jessie
Replies: 2
Views: 839

Kodi on Jessie

Does Kodi run on the basic Jessie version of Raspbian. I have installed it (sudo apt-get install kodi) and it seemed to install OK, but when I type Kodi nothing happens
by tdenson
Tue Feb 14, 2017 4:57 pm
Forum: Troubleshooting
Topic: All 16GB sd cards are not created equal
Replies: 6
Views: 1021

Re: All 16GB sd cards are not created equal

Thanks very much
by tdenson
Tue Feb 14, 2017 11:41 am
Forum: Troubleshooting
Topic: All 16GB sd cards are not created equal
Replies: 6
Views: 1021

All 16GB sd cards are not created equal

I have created a an sd card containing Jessie and lots of customisation I have done, which I now want to duplicate to a number of sd cards. The problem is that I have used a 16GB sd card which is larger than the average and dd gives an error when it falls of the end. I had hoped that there was nothi...
by tdenson
Sun Jan 29, 2017 12:12 pm
Forum: Automation, sensing and robotics
Topic: Is it possible to supply power via IO pins
Replies: 6
Views: 1003

Re: Is it possible to supply power via IO pins

Also, I've just spotted a massive flaw in my plan A - there's no easy way to power cycle
by tdenson
Sun Jan 29, 2017 12:10 pm
Forum: Automation, sensing and robotics
Topic: Is it possible to supply power via IO pins
Replies: 6
Views: 1003

Re: Is it possible to supply power via IO pins

No, I think I'll come up with a custom micro USB lead with a plug that connects to a socket on my PCB.
by tdenson
Sun Jan 29, 2017 11:22 am
Forum: Automation, sensing and robotics
Topic: Is it possible to supply power via IO pins
Replies: 6
Views: 1003

Re: Is it possible to supply power via IO pins

Probably not a good idea then. I was looking at mounting a Pi on a PCB and wanted to minimise the amount of physical wiring.

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