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by tlfong01
Tue Feb 19, 2019 8:25 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

... so you can use a larger gate resistor. The only change will be a slightly increased turn-on and turn-off times as the gate capacitance (1350pF from data sheet) will take longer to charge/discharge. I usually ignore the charging/discharging time for my Micky Mouse toy projects, switching on/off ...
by tlfong01
Tue Feb 19, 2019 8:20 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

Remember too that diodes are polarised ... The aim is to provide a short path for the "back EMF" produced by a coil (such as in a solenoid) when it is turned OFF --the current will try to continue as the magnetic field decays, which can produce a damaging reversed voltage if not removed by the diod...
by tlfong01
Tue Feb 19, 2019 8:15 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

1. notepad is indeed usable for this task. 2. the gate has also some (parasitic) capacitance, need to be charged and the Rpi will see it as a "short" circuit for a small amount of time. And the gate resistor will limit the current to a save value for the Rpi. 3. 1n4148 and if the solenoid is bigger...
by tlfong01
Tue Feb 19, 2019 8:09 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

The resistor between GPIO and gate ... 1k would be enough. So would 470 or 330 For the resistor from gate to source: doesn't really matter, but 10k would be good. Because the two resistors will form a potential divider, and you want the gate to go as high as possible, using 1k and 10k for those wou...
by tlfong01
Tue Feb 19, 2019 8:05 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

As far as a diode, same q: where, and...what size? I recommend 1N5822 for newbies. The leads are strong and not easily broken by careless newbies. I usually heavily soldered the flyback diode across the terminals at the MOSFET side, NOT across the solenoid (see my pictures in earlier posts). This w...
by tlfong01
Tue Feb 19, 2019 7:59 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

1. You can put a resistor in the GPIO - gate line; that will help protect the Pi if you connect things wrongly. 2. You can also connect a resistor between the gate and source, to hold the gate low 1. Rg = 470R for two purposes: (a) Current limiting, in case you set pin out put, but you incorrectly ...
by tlfong01
Tue Feb 19, 2019 7:52 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

theitguyfromny wrote:
Sat Feb 02, 2019 2:36 pm
So, I think I have all that right...but...do I need 1 or 2 or 84 resistors in that mix?

What do you mean by 84 resistors?
by tlfong01
Tue Feb 19, 2019 4:53 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

Logic Level Power MOSFET Solves The Problem Yes, IRF540 replaced by IRL540 or similar solves the problem. https://youtu.be/eXIxTtvtLaQ (youtube logic level power MOSFET driving motor and solenoid) Power MOSFET IRL540N Hacking Diary Last evening I ordered 50 pieces of IRL540N at ¥1.20/ea to be deliv...
by tlfong01
Tue Feb 19, 2019 3:13 am
Forum: Beginners
Topic: RPI Zero W multiple sensors
Replies: 27
Views: 2591

Re: RPI Zero W multiple sensors

So if you can indicate your time constraint or long term learning goal, say 1 year or 3 years , then I can suggest more things accordingly. i want to tell you what exactly i'm going to do. i want to start a business for planting MicroGreens, and there is no team involved, it's only me. my time fram...
by tlfong01
Tue Feb 19, 2019 3:02 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

... I failed English and so had to do Engineering ... No English No Engineer, Only Technician :( Oh my goodness. I failed English and so could not do engineering - tlfong01, the Super Technician . :mrgreen: Appendix - Graduates, do you know English? - McKinsey Graduates, do you have these job skill...
by tlfong01
Tue Feb 19, 2019 1:29 am
Forum: Beginners
Topic: Detect current on Raspberry pi
Replies: 88
Views: 8527

Re: Detect current on Raspberry pi

tlfong01 wrote:
Thu Jan 31, 2019 7:02 am

Motion Activated Security Camera with the Raspberry Pi Zero

Building a Motion Activated Security Camera with the Raspberry Pi Zero - Mark West 2018aug12
https://www.bouvet.no/bouvet-deler/utbr ... ry-pi-zero
by tlfong01
Mon Feb 18, 2019 2:31 pm
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

1. Well first this is the wrong mosfet when you have 3.3V for the gate. 2. I looked at your chart I see that it won't be able to switch the valve. Logic Level Power MOSFET Solves The Problem Yes, IR F 540 replaced by IR L 540 or similar logic level MOSFET solves the problem. https://youtu.be/eXIxTt...
by tlfong01
Mon Feb 18, 2019 12:07 pm
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

1. Well first this is the wrong mosfet when you have 3.3V for the gate. 2. I looked at your chart I see that it won't be able to switch the valve. If I look at my three irf540 only one was able to switch a small relay from gnd to 3.3V. 3. It is not because it works one that it will always work. IRF...
by tlfong01
Mon Feb 18, 2019 8:18 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

Power MOSFET driving big solenoids Now I am checking out if the power MOSFET can drive big solenoids. https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=230984&start=25#p1417772 Driving Big Motor Mabuchi RS-540SH 12VDC Motor I used Vgs 3V and 5V signal by hand to test 0.4N solenoid OK. Then I ...
by tlfong01
Mon Feb 18, 2019 7:17 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

tlfong01 wrote:
Mon Feb 18, 2019 5:03 am

Power MOSFET driving big solenoids

Now I am checking out if the power MOSFET can drive big solenoids.
https://www.raspberrypi.org/forums/view ... 5#p1417772
...
by tlfong01
Mon Feb 18, 2019 7:01 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

Rds(on) for 12V 5Ω 2A Load I increased the resistive load from 10Ωto 5Ω. I found the saturated Rds(on) increases from 30mΩto about 90mΩ , at saturated current of 1.75A, and Vds 0.05V . Power is 1.75 * 0.05 = 0.09W = 0.1W . My conclusion a current switch of logic 3V0 level control of 1.75A, 90mΩ , 0...
by tlfong01
Mon Feb 18, 2019 5:03 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

tlfong01 wrote:
Mon Feb 18, 2019 3:48 am
I found Rds(on) in the twilight zone is of the order 30mΩ. Now I am going to zoom in, to get a better picture of what the hell is going on there, ...

Rds(on) vs Vgs (2.6V ~ 10V)

/ to continue, ...

https://penzu.com/p/acc88f4b (big picture of twilight zone)

...
by tlfong01
Mon Feb 18, 2019 3:48 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

1. measure voltage across drain and source . 2. it should be a very small voltage low RDS(on). 3. can calculate what the real RDS(on) 4. compare value to datasheet . Twilight Zone Spec Actually I am trying to create a twilight zone spec where Vgs = Rpi Voh = 2.4V ~ 3.2V. This Vgs range is what I ho...
by tlfong01
Sun Feb 17, 2019 2:48 pm
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

tlfong01 wrote:
Sun Feb 17, 2019 2:08 pm

Rds(on) Measurement

https://penzu.com/p/acc88f4b
...
by tlfong01
Sun Feb 17, 2019 2:08 pm
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

1. simply need to measure the voltage across the drain and the source . And it should be a very small voltage across it . Because of the low RDS(on) value. 2. So, you can also calculate what the real RDS(on) 3. compare that value to the one in the datasheet. Rds(on) Measurement You guess is very co...
by tlfong01
Sun Feb 17, 2019 1:00 pm
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

@tlfong01 1. You can also measure how open or close the n channel is of the MOSFET. 2. You simply need to measure the voltage across the drain and the source . And it should be a very small voltage across it. Because of the low RDS(on) value. 3. So, you can also calculate what the real RDS(on) is a...
by tlfong01
Sun Feb 17, 2019 8:38 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

CSD18511KCS Preliminary Test Results The penzu journal entry below summaries the test results. My quick and dirty conclusion is the following. 1. Power MOSFET CSD18511KCS is fully compatible with Rpi 3V3 GPIO (direct drive) . 2. No gate driver is necessary. https://penzu.com/p/acc88f4b ( Test resul...
by tlfong01
Sun Feb 17, 2019 6:56 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

IRF540N Test Circuit IRF540N Test Circuit - With Rg and Rgs added https://penzu.com/p/087c1ca8 Your R2 (1k) has a to low value in comparison to your R1. So, you have made a voltage divider instead. And that is not what you want here. So, you need a higher value of R2. I have used values of 50k as a...
by tlfong01
Sat Feb 16, 2019 4:36 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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

I have ordered the right mosfet, logic level input, Vgs(th) 1.8V, Rpi friendly CSD18511KCS ¥3.20 each x 25 = ¥80 WaterFall/Agile Rpi3 Based Mini 4WD Smart Vehicle Incremental/Continuous Testing/Continuous System-Integration/Test Driven Development Plan https://penzu.com/p/acc88f4b / to continue, ...
by tlfong01
Fri Feb 15, 2019 2:17 pm
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 9549

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: There is nothing misleading about it. It is your misinterpretation of th...

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