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by ptimlin
Wed Apr 03, 2019 9:12 pm
Forum: Automation, sensing and robotics
Topic: Garden automation electronics schematic
Replies: 6
Views: 950

Re: Garden automation electronics schematic

Hi again, So a quick look and I don't see anything too concerning. To answer your original questions. 1) yes I would go with the MOSFET over the TIP120 in this application. Even at lower currents the TIP120 (a BJT (bipolar junction transistor) would likely require a heatsink where as the MOSFET is p...
by ptimlin
Wed Apr 03, 2019 7:50 pm
Forum: Automation, sensing and robotics
Topic: Know where I can get reasonably priced DPST/DPDT 240v/8a to 240v/10a relays?
Replies: 16
Views: 1842

Re: Know where I can get reasonably priced DPST/DPDT 240v/8a to 240v/10a relays?

Those little relays are nice, but (1) are only single pole (we really need two) and (2) will not cope with the inrush current of the big SMPSs it's going to be switching. They can have an inrush measured in tens of amps. A Dell server I know with a similar power requirement is specified to have not...
by ptimlin
Wed Apr 03, 2019 6:58 pm
Forum: Automation, sensing and robotics
Topic: Know where I can get reasonably priced DPST/DPDT 240v/8a to 240v/10a relays?
Replies: 16
Views: 1842

Re: Know where I can get reasonably priced DPST/DPDT 240v/8a to 240v/10a relays?

Thanks - that's more or less what I'm finding. My reasonable price would be to stay around $50-$75 for the 16 relays. I mean - when you can get 16 SPDT relays rated for 250V/10A on a PCB with optocouplers, LED indicators, etc... for a total of $15 - $18 per relay seems unreasonable. I mean, It's a ...
by ptimlin
Wed Apr 03, 2019 6:30 pm
Forum: Automation, sensing and robotics
Topic: Garden automation electronics schematic
Replies: 6
Views: 950

Re: Garden automation electronics schematic

Do you have an actual schematic you can share (the photo you posted is a wiring diagram)? Hard to comment when you can not see which components are being used in the design.
by ptimlin
Wed Apr 03, 2019 6:25 pm
Forum: General discussion
Topic: 3.3v Relay Exists?
Replies: 7
Views: 4779

Re: 3.3v Relay Exists?

while you dont want to hear it, a relay isnt the best component to switch a small dc load, your much better off looking at a mosfet solution. a relay is an AC switching component . I do not fully agree with this statement. A relay is also commonly used in the automotive industrie. For example, ther...
by ptimlin
Tue Apr 02, 2019 4:53 pm
Forum: Beginners
Topic: Input Relay Board
Replies: 22
Views: 1594

Re: Input Relay Board

1 Three way 220/120 ac voltage monitoring unit £ 12.00 1 220 / 110 vac Relay £10.00 x 3 = £ 30.00 Sounds like he only needs two. So £ 20 for the relays ;) No cost of relays mounting box No AC relay buzz or noise How is it that you require a box for the relays but not one for this exposed circuit bo...
by ptimlin
Tue Apr 02, 2019 12:53 am
Forum: Automation, sensing and robotics
Topic: Know where I can get reasonably priced DPST/DPDT 240v/8a to 240v/10a relays?
Replies: 16
Views: 1842

Re: Know where I can get reasonably priced DPST/DPDT 240v/8a to 240v/10a relays?

If you shop places like Digi-Key or Grainger and other trust worthy vendors you know you are not buying cheap knock off junk from China. Not sure what you hope to be a "reasonable" price, but you should be able to find DPDT relays that can switch 240V/10A for about $18-ish US each. But as you mentio...
by ptimlin
Tue Apr 02, 2019 12:38 am
Forum: Beginners
Topic: Input Relay Board
Replies: 22
Views: 1594

Re: Input Relay Board

And what powers the relay contacts and opto input? Ya if I were to use a 120Vac activated relay to sense is the 120V is on or not, then stupid easy way to do it is have the contacts simply connect the Pi's 3.3V to a GPIO input pin. No optoisolator or other components requires. The contacts are alre...
by ptimlin
Mon Apr 01, 2019 7:33 pm
Forum: Beginners
Topic: Input Relay Board
Replies: 22
Views: 1594

Re: Input Relay Board

ptimlin: Sorry but the seller (and google) have not provided any schematics or instructions for this board. I did request them but did not get a response so I'll have to figure this out the hard way. Since you have it in your hands, you can tell us what ICs are on it and how the components are hook...
by ptimlin
Mon Apr 01, 2019 2:59 am
Forum: Beginners
Topic: Input Relay Board
Replies: 22
Views: 1594

Re: Input Relay Board

I will repeat my original question since it was not answered. Did this device/board come with any sort of schematic, data sheet, or other documentation? That would be very helpful. As to the "active low", I explained it here somewhere a little while ago, but too lazy to look for it. Answer is that i...
by ptimlin
Sun Mar 31, 2019 8:57 pm
Forum: Beginners
Topic: Input Relay Board
Replies: 22
Views: 1594

Re: Input Relay Board

There was no schematic or data sheet supplied with the board? If I had to guess I would assume that the output on the Pi side will be whatever voltage you use to supply the board's VCC & GND. Since the description indicates 3-5V use I would think if you supply 3.3V to the Vcc pin then you will get 3...
by ptimlin
Sun Mar 31, 2019 8:45 pm
Forum: Automation, sensing and robotics
Topic: raspberry pi connect button problem
Replies: 4
Views: 500

Re: raspberry pi connect button problem

At a guess, the other pins labelled + and - are for an in-built LED and can be ignored. Agreed. This is a lighted button and if the original poster wants to just use the switch then they need "C" and then at least one other of the NC or NO terminals. "C" all by itself, as in the original post, does...
by ptimlin
Sun Mar 31, 2019 8:18 pm
Forum: Automation, sensing and robotics
Topic: How best to control higher voltage relays with 12v/24v coils?
Replies: 26
Views: 3327

Re: How best to control higher voltage relays with 12v/24v coils?

If I might make a suggestion. Will use Digi-Key links but you can probably find these parts elsewhere... ULN2003LV (must be the "LV" version to interface directly with the Pi GPIO) are 70-cents and can drive 7 relays. https://www.digikey.com/product-detail/en/texas-instruments/ULN2003LVDR/296-30403-...
by ptimlin
Sat Mar 30, 2019 9:22 pm
Forum: General discussion
Topic: 6.5 inch touch screen for Raspberry Pi 3
Replies: 12
Views: 2258

Re: 6.5 inch touch screen for Raspberry Pi 3

The screen I mentioned above only needs the GPIO bus if you want to use the touch screen. Otherwise it works fine as a generic HDMI screen with no drivers required. You will have to apply power to the USB plug on it or apply power through the header that normally would connect to the GPIO.
by ptimlin
Wed Mar 27, 2019 3:27 pm
Forum: Automation, sensing and robotics
Topic: Septic/Sump Automation Project
Replies: 5
Views: 843

Re: Septic/Sump Automation Project

Nice project. I will book mark it and look at it more closely later. I actually got my Raspberry Pi last Christmas (I put it on my Amazon wish list) specifically for exactly this same project. I have a sump pump in my basement with a french drain system that runs pretty much constantly towards the e...
by ptimlin
Wed Mar 27, 2019 2:56 pm
Forum: General discussion
Topic: 6.5 inch touch screen for Raspberry Pi 3
Replies: 12
Views: 2258

Re: 6.5 inch touch screen for Raspberry Pi 3

How about a 5" screen? Sorry for the American Amazon link but I got this one... https://www.amazon.com/dp/B01FQBPDIG/?coliid=I2HKGK4827V7UM&colid=181XG5BPMZHIQ&psc=0&ref_=lv_ov_lig_dp_it which is available under a range of brand names and prices (I paid $25 US for this one which now shows as $38 US)...
by ptimlin
Sat Mar 23, 2019 8:41 pm
Forum: Automation, sensing and robotics
Topic: switching wall light on/off causes GPIO interrupt
Replies: 11
Views: 3042

Re: switching wall light on/off causes GPIO interrupt

I would suggest first determining where the interference is getting into your Pi. Most likely it is through the house wiring, into your power supply, and then into the Pi. But there could be a remote change it is coming from radio frequencies in the air. Simple test is to run the Pi off a battery pa...
by ptimlin
Thu Mar 21, 2019 7:26 pm
Forum: General discussion
Topic: Pi 3B male 40 pin header - gold, nickel or tin plating?
Replies: 15
Views: 1621

Re: Pi 3B male 40 pin header - gold, nickel or tin plating?

However, it will force us to buy 2 connector types (Gold and Tin plating ) to match the batch of Pi modules at the time of manufacture. This increases our parts cost. (Phosphor bronze is copper-tin alloy and is compatible with tin plating). The long term effects are what I am concerned about. We pl...
by ptimlin
Wed Mar 13, 2019 4:45 pm
Forum: Beginners
Topic: Mini keyboard - buy or make?
Replies: 7
Views: 1300

Re: Mini keyboard - buy or make?

I got the keyboard but it doesn't work when wired only. It's charging, but still needs bluetooth. Not a solution for me When wired did you turn it on too? On the one of mine I used wired I did have to still turn it to ON for it to worked wired. Might be difference models act differently. I have two...
by ptimlin
Mon Mar 11, 2019 4:42 pm
Forum: Automation, sensing and robotics
Topic: Remote control Relays?
Replies: 1
Views: 319

Re: Remote control Relays?

I don't know how to do it, but it would seem to me if your controller can access Dropbox and download files, then wouldn't it be easier to simply remotely connect to the Pi directly instead, say through a secure shell (SSH)?
by ptimlin
Sun Mar 10, 2019 8:28 pm
Forum: Python
Topic: How to test encoder with raspberry Pi
Replies: 33
Views: 3027

Re: How to test encoder with raspberry Pi

Actually sparkyhall's statement about the outputs being "TTL/RS422" is somewhat confusing. TTL and RS422 are very different. I just assumed the manufacturer was saying you could use the encoder with TTL where you would only use two lines A and B and (or /A and /B if you prefer) referenced to circui...
by ptimlin
Fri Mar 08, 2019 2:35 pm
Forum: General discussion
Topic: Under voltage detected - revisited
Replies: 26
Views: 2884

Re: Under voltage detected - revisited

Possibly the schematic is not quite true, and the board is putting the 5V supply to the board through D1 before passing it to the Pi, so your Pi is actually getting 5.02V minus a diode drop. I am not seeing that. I think you are looking at it backwards. To me it looks like you plug the Pi into this...
by ptimlin
Fri Mar 08, 2019 2:18 pm
Forum: General discussion
Topic: 480x320 screen for the raspberry pi zero w?
Replies: 5
Views: 380

Re: 480x320 screen for the raspberry pi zero w?

Does this screen use all the GPIO pins? It only ties up 6 of the pins to do its thing but the way it is designed you plug it on over your Pi which covers ALL the pins. So they have provided a side breakout board part that brings the connection out to the side on another connector to allow you to st...
by ptimlin
Thu Mar 07, 2019 6:45 pm
Forum: Python
Topic: How to test encoder with raspberry Pi
Replies: 33
Views: 3027

Re: How to test encoder with raspberry Pi

Do you have a volt meter? You can read the output of the encoder when it isn't moving then very slowly turn it and see if it changes state. Also when you turn it and stop you should randomly get it to settle on a high or low. If you turn it and never see it randomly go high or low, you might have a ...
by ptimlin
Mon Mar 04, 2019 12:50 am
Forum: Automation, sensing and robotics
Topic: python with pushover
Replies: 3
Views: 837

Re: python with pushover

pcmanbob wrote:
Sun Mar 03, 2019 10:11 am
So what was so hard about that ? :? :?
Nothing. He posted the vague question and you did all the work. So looks like it wasn't hard for him at all. ;)

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