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by ptimlin
Fri Jan 08, 2021 8:30 pm
Forum: Automation, sensing and robotics
Topic: How to run encoder motor with motor driver and raspberry pi
Replies: 3
Views: 434

Re: How to run encoder motor with motor driver and raspberry pi

juskirat2000 wrote:
Tue Jan 05, 2021 3:54 pm
Thank you very much for your reply. Is it possible that if you could explain to me the connections to make for the complete circuit?
So you can not even be bothered to answer his question to you (see the very first line of his reply) yet you want him to whip up a full schematic for you?
by ptimlin
Fri Jul 31, 2020 1:47 pm
Forum: Automation, sensing and robotics
Topic: Automatic Car Battery Cut off to prevent rundown andAAA call
Replies: 50
Views: 15470

Re: Automatic Car Battery Cut off to prevent rundown andAAA

I have owned 3 car and run them for the last 25 years and I had about 15 batteries replaced I think those two statements pretty much sum up this person's knowledge of and ability to upkeep a basic lead acid battery. I hope he isn't paying for those long life 5+ year batteries since he only gets an ...
by ptimlin
Fri Jan 03, 2020 9:07 pm
Forum: Beginners
Topic: Controlling bi-color LED with two leads.
Replies: 7
Views: 980

Re: Controlling bi-color LED with two leads.

I don't see anything in gpiozero documentation on how to do the high/low. Only see one lead on ground and sending the on/off to the other lead. Does gpiozero not have the capability for this? ON/OFF = High/Low. And instead of tying one side of the lED to ground, tie it to the other GPIO pin. As alr...
by ptimlin
Tue Dec 31, 2019 2:37 pm
Forum: Beginners
Topic: Voltage Drop with 2.5amp 5v supply
Replies: 7
Views: 937

Re: Voltage Drop with 2.5amp 5v supply

However when the pi is under load it drops to 4.83 and that is when the pi starts complaining. First thing to figure out is where is the voltage drop occurring. Put your meter across the output of the step down regulator and then run it so you get the low voltage warning. Do you see the same 4.83V ...
by ptimlin
Mon Aug 12, 2019 2:10 pm
Forum: Automation, sensing and robotics
Topic: Relay Question
Replies: 2
Views: 1152

Re: Relay Question

Agreed. The relay you have can be used to as an interface between the Pi and your power relay. For a power relay, stick to name brands like Omron and their data sheets will typically give you complete specs including for switching AC and DC loads as well as sometimes showing resistive and inductive ...
by ptimlin
Wed Jun 12, 2019 3:21 pm
Forum: Automation, sensing and robotics
Topic: Help trying to control 3v relay using GPIO?
Replies: 4
Views: 638

Re: Help trying to control 3v relay using GPIO?

How much current does the relay coil need to operate properly. By my calculation, your transistor circuit is only guaranteed to be able to supply a minimum of about 126mA to the relay coil. If the coil requires more than that, this could the problem. Solution to get more current for the relay coil i...
by ptimlin
Wed Jun 12, 2019 3:12 pm
Forum: Teaching and learning resources
Topic: Learning Basic Electronics
Replies: 9
Views: 7871

Re: Learning Basic Electronics

I will add your local library may already be subscribed to some online learning sites. For example, my local (USA based) library subscribed to Lydia.com where there are a ton of education videos and tutorials including things like electricity/electronics and Python. Go to your libraries web site and...
by ptimlin
Fri May 31, 2019 8:39 pm
Forum: Automation, sensing and robotics
Topic: Detecting 250VAC voltage/current of deep well pump motor
Replies: 45
Views: 21770

Re: Detecting 250VAC voltage/current of deep well pump motor

The wall wart's output is rated for 3v3 at 2 amps. It does seem like a lot of juice to dissipate for what I'm trying to do. One quick and dirty method to dissipate the wall-wart energy is to put a low resistance across the output (tens of ohms). Then to the Pi you feed this through a diode to isola...
by ptimlin
Tue May 28, 2019 9:10 pm
Forum: Automation, sensing and robotics
Topic: Detecting 250VAC voltage/current of deep well pump motor
Replies: 45
Views: 21770

Re: Detecting 250VAC voltage/current of deep well pump motor

I found that I can get to 3v3 with R1: 1700 and R2: 3300. How would I integrate the 10K pulldown resistor to ensure the RPi GPIO doesn't float when the wall wart is not powered? You don't need a 10k pulldown. Output of charger is +5V, one side goes to the GND of your Pi. The other side goes through...
by ptimlin
Tue May 28, 2019 8:56 pm
Forum: Automation, sensing and robotics
Topic: LED Watt / Amp question
Replies: 3
Views: 987

Re: LED Watt / Amp question

Getting about 800-1000 lumens for 10W on LEDs sounds about right, so I am guessing the 10W is the real power being used by the LED light. I assume when you say you hooked up the transformer and the "lights" ran without the transformer getting hot, you were actually talking about ONE light?...
by ptimlin
Tue May 28, 2019 8:47 pm
Forum: Automation, sensing and robotics
Topic: how to control 24VDC valve with ULN2803A?
Replies: 25
Views: 7706

Re: how to control 24VDC valve with ULN2803A?

Just a design note that I think is important to know when working with the ULN2803A and others driver ICs of the same types (ULN2003, etc.) which I don't think was mentioned in this thread the first time around and worth mentioning since the new poster is wanting to drive 8 relays with a single IC. ...
by ptimlin
Mon May 20, 2019 7:08 pm
Forum: Automation, sensing and robotics
Topic: DS18B20: Influence of supply voltage on temperature
Replies: 21
Views: 5202

Re: DS18B20: Influence of supply voltage on temperature

that the almost certainly increased 'wasted' current flow with increased supply voltage through the circuitry around the sensor was heating it up, so that it was correctly reading a higher temperature. I still don't think so. These sensors have been around for decades, long before Raspberry Pis exi...
by ptimlin
Sat May 18, 2019 6:18 pm
Forum: Automation, sensing and robotics
Topic: DS18B20: Influence of supply voltage on temperature
Replies: 21
Views: 5202

Re: DS18B20: Influence of supply voltage on temperature

But to answer your question, I am not sure why the change in Vdd to the sensor would change the temperature reading. Could it be something as simple as heating due to increased power dissipation in the sensor at the higher supply voltage? Scrubbing the data sheet for the sensor, there is nothing to...
by ptimlin
Wed May 15, 2019 5:37 pm
Forum: Automation, sensing and robotics
Topic: DS18B20: Influence of supply voltage on temperature
Replies: 21
Views: 5202

Re: DS18B20: Influence of supply voltage on temperature

To confirm, you are running a three wire system where three separate wires run out to the sensor? And as rpdom asked, the pull up should remain between 3.3V and your GPIO line regardless if you power the sensor from 3.3V or 5V. Also is the pull up resistor next to the Pi or next to the sensor? I bel...
by ptimlin
Sun May 12, 2019 4:40 am
Forum: Beginners
Topic: Small part fell off my pi
Replies: 20
Views: 2273

Re: Small part fell off my pi

Most likely it is a small filter capacitor and your Pi will work fine without it.
by ptimlin
Thu May 02, 2019 7:36 pm
Forum: Beginners
Topic: Multiple LEDs - series, parallel, both?
Replies: 6
Views: 2218

Re: Multiple LEDs - series, parallel, both?

Just a few random observations that might answer some of your questions (I didn't carefully read everything you wrote so sorry if I am "answering" something you didn't ask. With the very first photo you are using PC817 opto couplers. The first mistake most of us make when we started to use...
by ptimlin
Thu May 02, 2019 6:48 pm
Forum: Other projects
Topic: Automate water heater - Temp sensor/110v relay/switch
Replies: 10
Views: 1993

Re: Automate water heater - Temp sensor/110v relay/switch

The Pi's GPIO pins are usually not up to the task of driving most mechanical relays and many solid state relays (SSR). Usually you will need some sort of interface between the two. What is the wattage of the heater you plan to use? I know you said "110V" at somewhere between 8-10 amps, but...
by ptimlin
Thu May 02, 2019 5:25 pm
Forum: Beginners
Topic: Controlling temperature chamber using Peltier and PWM signal with external power source
Replies: 26
Views: 5958

Re: Controlling temperature chamber using Peltier and PWM signal with external power source

Would you mind giving me direction on how to select the proper type of Peltier for heating purposes? :) Thank you! Sorry for my many questions! As others have mentioned, if you only need to heat and not cool, then a peltier is an overly complicated way to do it. Just use heating elements instead. T...
by ptimlin
Thu May 02, 2019 4:50 pm
Forum: Automation, sensing and robotics
Topic: Outdoor Pond Water Level Control / Valve
Replies: 9
Views: 1680

Re: Outdoor Pond Water Level Control / Valve

While I can appreciate if the idea is to learn to use the Pi for something like this then I say have at it. But if the idea is simply to get an auto top off for the ponds, any reason why you can not use plain old mechanic float switches that simply open or close a water valve? Search for something l...
by ptimlin
Thu May 02, 2019 3:51 pm
Forum: Automation, sensing and robotics
Topic: Sump pump alarm
Replies: 4
Views: 1987

Re: Sump pump alarm

I have been thinking about a project along the same lines. A couple of things I have thought about you may also want to consider. One reason a sump will fill too high is because of a power outage and no way to run the sump pump. This would mean without extra battery power for various components (Pi ...
by ptimlin
Sat Apr 06, 2019 6:20 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: 2370

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

TL;DR past paragraph one. So will only comment on one part of paragraph one. You wrote: "Most of the companies producing end-user electronics are doing so via China - yet the Chinese relays can't be trusted?" We are not talking about components manufactured in China for known brands with g...
by ptimlin
Sat Apr 06, 2019 6:09 pm
Forum: Automation, sensing and robotics
Topic: How best to control higher voltage relays with 12v/24v coils?
Replies: 26
Views: 5478

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

Quick clarification question. You mentioned you would need to have all 16 relays on at the same time. Is this always the case (all on or all off)? Or are their times when you would need to individually control some of them? If it is all on or all off, then you can simplify the entire design by drivi...
by ptimlin
Fri Apr 05, 2019 3:43 pm
Forum: Automation, sensing and robotics
Topic: Wiring relay to Pi
Replies: 27
Views: 5749

Re: Wiring relay to Pi

So the 15-20mA is the current required to switch the actual relay ie current drawn by the coil. this is being switch be the transistor on the relay board, so all we are doing it switching this transistor on using the opto isolator so it should only require a few mA to switch that transistor, but as...
by ptimlin
Fri Apr 05, 2019 3:36 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: 2370

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

A couple of points. One, relays are much more than simply a coil and some contacts. A lot of R&D goes into developing relays and there is a WIDE range of technologies and materials used in various relays, even if they all just say "DPDT" in the specification. So the better relays are n...
by ptimlin
Fri Apr 05, 2019 3:24 pm
Forum: Automation, sensing and robotics
Topic: How best to control higher voltage relays with 12v/24v coils?
Replies: 26
Views: 5478

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

The ULN2803A could work as well. The thing to keep in mind is that this one is a Darlington configuration so you might lose as much as a voltage on the output so that when you pull the output low it may only get down to 1V or so when pulling a hundred milliamps or more. So keep that in mind of drivi...

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