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by ptimlin
Sun Mar 03, 2019 7:56 pm
Forum: Beginners
Topic: Monitoring Relay Status - Pull down / Pull up and best way to do?
Replies: 2
Views: 179

Re: Monitoring Relay Status - Pull down / Pull up and best way to do?

Hi, Nice project. One that I might take on as I have been thinking about just such a system for my aquariums for many years now. I am brand new to the Pi world, so I am learning about it now. Anyway, some general comments on your approach if I may... What ever you decide to do, one thing you want to...
by ptimlin
Wed Feb 27, 2019 8:44 pm
Forum: Beginners
Topic: GPIO programming question
Replies: 5
Views: 270

Re: GPIO programming question

B.Goode wrote:
Wed Feb 27, 2019 8:34 pm
Your Truth table does not seem to coincide with your written description.
It is a truth table for no power to your Pi.


;)
by ptimlin
Wed Feb 27, 2019 8:43 pm
Forum: Beginners
Topic: LED connected to 3.3V and GPIO (output,HIGH) no ground
Replies: 8
Views: 406

Re: LED connected to 3.3V and GPIO (output,HIGH) no ground

Being new to this stuff, my brain just has trouble wrapping around providing positive voltage to both the anode and the cathode of an LED as a means of negating current flow. It seems much more intuitive to just not provide current when it's not needed than to output current on both sides. Is one w...
by ptimlin
Mon Feb 25, 2019 9:11 pm
Forum: Beginners
Topic: PCB connector crimp tool.
Replies: 5
Views: 335

Re: PCB connector crimp tool.

While not really cheap for hobbyists, I swear by my Molex hand crimper, p/n 63811-1000 ... https://www.digikey.com/products/en?keywords=63811-1000 There is very few contacts I can not crimp with it, certainly well enough for one off things. And while costing close to $60 US, it is indestructible and...
by ptimlin
Thu Feb 21, 2019 4:35 pm
Forum: Beginners
Topic: Different GPIO Pins?
Replies: 16
Views: 1216

Re: Different GPIO Pins?

drgeoff wrote:
Thu Feb 21, 2019 1:32 pm
-1

Resistive dividers are fine for RPI GPIOs. Unless you also need isolation.

Agreed. There is no "guesswork" involved with Ohm's Law. It is as straight forward and predictable as you can get.
by ptimlin
Mon Feb 18, 2019 11:38 pm
Forum: General discussion
Topic: All my RPIs 3 are underpowered, all the time
Replies: 23
Views: 1085

Re: All my RPIs 3 are underpowered, all the time

Just to be sure, you are not running three Pi units off of a single power supply are you?
by ptimlin
Mon Feb 18, 2019 6:46 pm
Forum: General discussion
Topic: 5v relay 1=0, 0=1?
Replies: 5
Views: 292

Re: 5v relay 1=0, 0=1?

MuntyScruntfundle wrote:
Mon Feb 18, 2019 2:26 pm
Also explains very well why I couldn't find any OR gates that didn't require external power I guess.
Look up Diode wired OR and AND gates if you want to get some idea how to make simple AND or OR gates with as many inputs as needed using diodes.
by ptimlin
Sun Feb 17, 2019 6:48 pm
Forum: Automation, sensing and robotics
Topic: Level sensor and valve combo
Replies: 4
Views: 463

Re: Level sensor and valve combo

As I recently mentioned in another thread around here, you might be able to utilize a solid state relay (SSR) that is designed to switch AC loads but run your DC solenoid through it. You can pick a SSR that has a 3.3V Pi friendly input trigger. The trick here is that when you run DC through an AC ou...
by ptimlin
Sun Feb 17, 2019 3:30 am
Forum: Beginners
Topic: Mini keyboard - buy or make?
Replies: 8
Views: 638

Re: Mini keyboard - buy or make?

Try one of these types... https://www.ebay.com/itm/USRobotics-USR5502-Portable-Mini-Bluetooth-Keyboard-for-Tablet-Smartphone-PC/272289786582?hash=item3f65bc6ad6:g:DLUAAOSwPNhcS6TF:sc:USPSFirstClass!01886!US!-1:rk:6:pf:0 or https://www.ebay.com/itm/Mini-Wireless-Bluetooth-3-0-Keyboard-for-iPad2-3-4-i...
by ptimlin
Sun Feb 17, 2019 3:17 am
Forum: General discussion
Topic: PiZero GPIO Pin Issues
Replies: 20
Views: 623

Re: PiZero GPIO Pin Issues

Ya I was going to say I could see some cold solder joints from your photos and that also reflowing them would likely fix the issue, which you have done. Congrats. A tip on soldering. What some beginners do is they put the tip on the solder pad only which makes the pad hot but the pin stays cold. Whe...
by ptimlin
Fri Feb 15, 2019 2:40 pm
Forum: Automation, sensing and robotics
Topic: Fuse between motor driver board and power source?
Replies: 12
Views: 861

Re: Fuse between motor driver board and power source?

A 20A fuse for your project will be useless. Both your motors on your project as well as AA batteries will self limit current well before 20A. So if you have a short or a stall the motor will draw and the AA battery will deliver whatever current they can until something else breaks or overheats. The...
by ptimlin
Fri Feb 15, 2019 2:18 pm
Forum: Beginners
Topic: Light Control Reef Tank
Replies: 3
Views: 153

Re: Light Control Reef Tank

I guess the question is, is this post about help with hardware or help with the Python programming only (SW only post)?
by ptimlin
Wed Feb 13, 2019 7:27 pm
Forum: Beginners
Topic: gpio led indication during boot
Replies: 6
Views: 286

Re: gpio led indication during boot

hey there! i have a question, is it possible to accesses the gpio when powering up the rpi, meaning before the boot has been completed? im working on an embedded system that needs about 9 sec. to boot up and id like to have some leds blinking during the waiting time :) So you basically just want so...
by ptimlin
Wed Feb 13, 2019 7:02 pm
Forum: Beginners
Topic: Raspberry Relay
Replies: 3
Views: 181

Re: Raspberry Relay

My guess is that both of you are using a Solid State Relay (SSR) and a lot of them are not designed to switch DC loads. They are for switching AC loads only. So look at the specification of your relay or relay board and see what the output specs say or look near the output terminals/pins of the devi...
by ptimlin
Tue Feb 12, 2019 8:26 pm
Forum: Beginners
Topic: RPI Zero W multiple sensors
Replies: 27
Views: 2437

Re: RPI Zero W multiple sensors

One suggestion is to look into the use of multiplexers (mux) and de-multiplexers (de-mux), both usually can be found in DIP package ICs so easy to breadboard, to allow your Pi to access more sensors with less pins. As an example, right now you have four load cells with each one requiring two of your...
by ptimlin
Tue Feb 12, 2019 7:00 pm
Forum: General discussion
Topic: 5v relay 1=0, 0=1?
Replies: 5
Views: 292

Re: 5v relay 1=0, 0=1?

To expand the answer a bit as to why, a billion years ago (or maybe a bit less) with early ICs, most chips could sink (pin goes low tied to ground through a transistor) a lot more current than they could source (output going high and requiring the pin to be the drive voltage). Also some ICs utilized...
by ptimlin
Tue Feb 12, 2019 4:22 pm
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9019

Re: Resistors and MOSFETs and fire-prevention, oh my

OK I have to ask, is tlfong01 some sort of weird automated BOT designed to analyse posts and then make up almost related responses, but not quite correct because a BOT doesn't truly understand what it is reading? :?: :mrgreen: But I am very serious when trying to point out that many electronic produ...
by ptimlin
Sat Feb 09, 2019 6:38 am
Forum: General discussion
Topic: Is Raspberry Pi capable of replacing 2 wire thermostat
Replies: 8
Views: 728

Re: Is Raspberry Pi capable of replacing 2 wire thermostat

You could consider two pis (Pi0Ws would do). One in the boiler cupboard where there's presumably power, one out in the hallway or wherever you want to measure temperature. This way they could both be located near power outlets. What for? If you are going to put one up where the thermostat is and pl...
by ptimlin
Fri Feb 08, 2019 11:24 pm
Forum: General discussion
Topic: Is Raspberry Pi capable of replacing 2 wire thermostat
Replies: 8
Views: 728

Re: Is Raspberry Pi capable of replacing 2 wire thermostat

Ya the problem is you typically do not have 24Vac AND the return for that transformer and without both you can not power the Pi (or whatever board you wanted to use) off just those two wires. You get 24Vac coming into the thermostat and when it closed it simply sends that 24Vac back down to the heat...
by ptimlin
Fri Feb 08, 2019 11:08 pm
Forum: General discussion
Topic: Capacitor ripped off of RPi 3 B+
Replies: 7
Views: 515

Re: Capacitor ripped off of RPi 3 B+

In general most capacitors like that are filter capacitors used to filter out high frequency noise from the power supply into your various ICs. If all is working well then you are likely fine to use it as is. If possible, you can always try reattaching the same capacitor down (unless you lost it) bu...
by ptimlin
Wed Jan 23, 2019 2:34 am
Forum: Automation, sensing and robotics
Topic: Line following sensor overheating
Replies: 2
Views: 282

Re: Line following sensor overheating

And do you have any kind of datasheet or schematic for the line following sensor? I looked at the CamJam web site and I can see the photo of the board on their kit but their site doesn't seem to have any downloadable data or schematic for how that particular sensor board should be wired up.
by ptimlin
Mon Jan 21, 2019 3:58 pm
Forum: Beginners
Topic: Servo without breadboard
Replies: 16
Views: 1277

Re: Servo without breadboard

Are you saying I could run a basic servo (like in my original post) straight from the Pi without an extra board/power supply? I thought external power = more torque? As my previous posts I'm not that familiar on the hardware front of things, could I connect a servo directly to the ESP8266 with powe...
by ptimlin
Mon Jan 21, 2019 3:08 pm
Forum: Python
Topic: Learn Python 2 or 3 and how?
Replies: 15
Views: 934

Re: Learn Python 2 or 3 and how?

Concur with the others, if you are just starting out, then start with the latest version, Python 3. For Android, I downloaded the SoloLearn app and am going through the Python 3 tutorial. Sometimes entering data on my Samsung S8 is a little funky on the quizes and such, but over all I have found it ...
by ptimlin
Mon Jan 21, 2019 4:33 am
Forum: Beginners
Topic: Reverse Polarity and Relay Board
Replies: 4
Views: 396

Re: Reverse Polarity and Relay Board

I hooked up 5V and ground to the power input and then 5V to the #1 relay with no effect at all. In my measuring I found that I get -5V rather than +5V when measuring between the 5V pin and GND. I checked the polarity on my multimeter about a million times. It's correct. Well without being able to s...
by ptimlin
Sun Jan 20, 2019 3:36 am
Forum: General discussion
Topic: Controlling an electric element.
Replies: 4
Views: 275

Re: Controlling an electric element.

This solid state relay should be able to handle it and should be able to be driven directly off a Pi GPIO pin if the limited data sheet (below) is correct... https://www.amazon.com/SSR-25-DC-AC-Solid-State-Relay/dp/B07FVR37QN/ref=asc_df_B07FVR37QN/?tag=hyprod-20&linkCode=df0&hvadid=241981127743&hvpo...

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