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by tlfong01
Sat Mar 02, 2019 1:25 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

So would this type of circuit work for it. Also from this circuit would I have to use both the GPIO pins and the relay or could I just use one? Using (1) small NPN BJT (eg 2N2222) and Relay or (2) Power NPN (eg TIP122 and no relay) or (3) Power MOSFET (eg IRL540N and no relay) So there are at least...
by tlfong01
Sat Mar 02, 2019 7:27 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

I tried to reduce R from 10k down to 1k, and then to 560R and 330R, I found Vr getting smaller, and there is also phase difference. However, when R reaches 330R, the sine wave has heavy distortion. I guess it is because too small L + R overloads the cheap function generator . ICL8038 Function Gener...
by tlfong01
Sat Mar 02, 2019 5:04 am
Forum: Automation, sensing and robotics
Topic: ADC sample rate (ADS1115)
Replies: 3
Views: 1336

Re: ADC sample rate (ADS1115)

You can look at increase the bus speed of the I2C see https://www.raspberrypi-spy.co.uk/2018/02/change-raspberry-pi-i2c-bus-speed/ Changing I2C Bus Speed Problem It appears that Rpi Spy's instruction only works for old Rpi models. For 3B+, no one knows how to change I2C bus speed :( RE: RASPBERRY P...
by tlfong01
Sat Mar 02, 2019 4:05 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

So would this type of circuit work for it. https://forum.allaboutcircuits.com/proxy.php?image=http%3A%2F%2Fimg4.hostingpics.net%2Fpics%2F483312transistorrelaysolenoidvalveflyback.png&hash=ecb29a13ff8e50f6fb20e7c79773d9f3 Also from this circuit would I have to use both the GPIO pins and the relay or...
by tlfong01
Sat Mar 02, 2019 3:57 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

Given that the time constant of an inductance and resistance is given by t=L/R, 100μH and 100k that gives 10ns, so you're not going to see much phase difference at frequencies much lower than 100MHz, ... R-L Time constant and phase differences etc Sir, actually I did not know that the L-R time cons...
by tlfong01
Sat Mar 02, 2019 3:10 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

1. What frequency is your sine-wave generator producing? 2. Given that the time constant of an inductance and resistance is given by t=L/R, 100μH and 100k that gives 10ns, so you're not going to see much phase difference at frequencies much lower than 100MHz 3. 100μH and 1k gives 100ns, so 10MHz ba...
by tlfong01
Sat Mar 02, 2019 2:26 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

1. What frequency is your sine-wave generator producing? 2. Given that the time constant of an inductance and resistance is given by t=L/R, 100μH and 100k that gives 10ns, so you're not going to see much phase difference at frequencies much lower than 100MHz 3. 100μH and 1k gives 100ns, so 10MHz ba...
by tlfong01
Fri Mar 01, 2019 2:46 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

Inductance Measurement Trail #1 So I setup the hardware and blindly selected R = 10k. But there is no phase difference between Vs and Vr. :( Inductance Measurement Trail #1 = Total Failure! :( I found Vr = Vs, same amplitude and phase, and I could not do any adjutments to make Vr not equal to Vs. A...
by tlfong01
Fri Mar 01, 2019 8:15 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

How to measure inductance - Rose-Hulman https://www.youtube.com/watch?v=ajycdvKyCEw Inductance Measurement Trail #1 So I setup the hardware and blindly selected R = 10k. But there is no phase difference between Vs and Vr. :( I guess the lazy student has not paid attention in the Rose Hullman classe...
by tlfong01
Fri Mar 01, 2019 5:02 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

Inductance Stuff - Hard to Understand, But Very Easy to Google, Cut, Paste, and Blindly Calculate So now I have read the references, watch the videos but still not thoroughly understand the weird phasors thing, but I think I am comfortable to start do the tests to find the inductance of my electrom...
by tlfong01
Fri Mar 01, 2019 1:37 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

... many people often disagree with me, So watch this space. I say high, you say low Well, I say build a wall, you say fire a rocket, I say leave, you say stay, ... So I am watching a rocket to fly over my head, and I will make a wish. :( Yes, this is life, la-la-la, la-la-la :mrgreen: Hello, Goodb...
by tlfong01
Fri Mar 01, 2019 1:11 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

jadel wrote:
Wed Feb 27, 2019 11:08 am
but can't a relay switch do the same thing, ...
what would be the advantage of using the FET system

Relay vs Power MOSFET vs Power NPN BJT

Well, it depends on 101 things. Perhaps you can let me know more about yourself and your project, to narrow down to, say, 10 questions.
by tlfong01
Thu Feb 28, 2019 2:57 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

Part 3 (Point 7) The lifting force is not easy to calculate . This is the part I found interesting. I am thinking of googling more readings and try to begin with calculating the inductance of solenoid or electromagnet which is useful for selecting a flyback diode. Inductance Stuff - Hard to Underst...
by tlfong01
Thu Feb 28, 2019 8:37 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

The problem is that we don't know the inductance of OP's electromagnet. Once we have got the inductance, then we can calculate the energy stored in the coil, and select a flyback diode with the appropriate current limit, breakdown voltage, and thermal capacity etc, ... Learning how to find the indu...
by tlfong01
Thu Feb 28, 2019 7:18 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

1. How short is "short"? 2. We don't know the inductance of the coil, so we don't know the time constant L/R 3. What is the main cause of the death of a diode? Assuming it's the maximum temperature that kills it, we would need to know its thermal capacity as well as how fast it can lose heat to the...
by tlfong01
Thu Feb 28, 2019 7:04 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 8976

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

Vin = 2.0V and Conclusion For power MOSFET IRL540N, the channel seems to almost completely closed at Vin ~= Vgs ~= 2V. At Vgs = 5V, 12V 5R 1kHz 50% duty cycle, rms current = 850 mA, dropping to about 800mA at Vgs = 4V, 3V. My quick and dirty conclusion (based on one and only one sample :mrgreen: ) ...
by tlfong01
Thu Feb 28, 2019 6:52 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 8976

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

tlfong01 wrote:
Thu Feb 28, 2019 6:50 am

Vin = 2.5V
...
by tlfong01
Thu Feb 28, 2019 6:50 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 8976

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

tlfong01 wrote:
Thu Feb 28, 2019 6:49 am

Vin = 3V
...
by tlfong01
Thu Feb 28, 2019 6:49 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 8976

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

tlfong01 wrote:
Thu Feb 28, 2019 6:47 am
Vin = 4V
...
by tlfong01
Thu Feb 28, 2019 6:47 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 8976

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

tlfong01 wrote:
Wed Feb 27, 2019 9:38 am
tlfong01 wrote:
Wed Feb 27, 2019 9:27 am
No Ringing Even Rg = 30R or 0R (no Rg)
No Cgs Charging or Discharging Problem Even Rg = 0 (Rgs = 4k7)
Testing Vgs 2V ~ 7V 1kHz square wave signal to IRL540N 12V 5Ω
Now I testing 1kHz 2Vpp to 7Vpp signal for IRL540N.
...

Vin = 5V
...
by tlfong01
Thu Feb 28, 2019 2:08 am
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

We don't know what jadel's "10A, 45V diode" is, It is a 10SQ045: http://www.senocn.com/data/PDF/10SQ030-10SQ100.pdf Would it still work? 10SQ045 vs 1N5822 Oh my goodness, your Schottky guy is 3 times stronger than mine. :mrgreen: 10SQ045 vs 1N5822 https://penzu.com/p/377d4751 TaoBao 10SQ045 - ¥3.5 ...
by tlfong01
Wed Feb 27, 2019 2:11 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

ICL8038 Mid Low Frequency (450kHz) Sinusoidal and Triangular Signal Generator - ¥16 https://item.taobao.com/item.htm?spm=a1z1r.7974869.0.0.269c3ad4UU9ZFc&id=568114234655 Sine/Triangle/Rectangular Wave Sig Gen Now I am trying to use the cheapy US$3 sig gen to find the inductance of solenoids, soleno...
by tlfong01
Wed Feb 27, 2019 1:44 pm
Forum: Automation, sensing and robotics
Topic: Connecting electromagnet to pi
Replies: 94
Views: 3960

Re: Connecting electromagnet to pi

DC12V 0.25A 3W Electromagnet Can Lift/Hold 2.5kg If 12V, 0.25A, 3W can lift 2.5kg, and power is proportional to square of current, your 6A should be able to lift (6 * 6) / (0.25 * 0.25) * 2.5kg = 1,440kg! Is my calculation is dodgy? 1. Yes, your calculation is dodgy . 2. What it "can lift" is nothi...
by tlfong01
Wed Feb 27, 2019 9:38 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 8976

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

tlfong01 wrote:
Wed Feb 27, 2019 9:27 am
No Ringing Even Rg = 30R or 0R (no Rg)
No Cgs Charging or Discharging Problem Even Rg = 0 (Rgs = 4k7)

Testing Vgs 2V ~ 7V 1kHz square wave signal to IRL540N 12V 5Ω

Now I testing 1kHz 2Vpp to 7Vpp signal for IRL540N.
...
by tlfong01
Wed Feb 27, 2019 9:27 am
Forum: Beginners
Topic: Resistors and MOSFETs and fire-prevention, oh my
Replies: 156
Views: 8976

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

Now I tested a 5 resistor 20W, and found everything OK. No Ringing Even Rg = 30R or 0R I decreased Rg fom 1k2 to 0R, but disappointedly did not see any ringing. What I don't understand is that smaller Rg means longer Cgs charging up time, not sure is because the Miller period is longer. ...

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