I really wouldn't recommend relying on the solder to hold the MOSFET to the 2-pin header; just stick the MOSFET pins directly into the machined-pin sockets. Or solder some short lengths of stranded hook-up wire between the MOSFET and the 2-pin header; let the wire flex, rather than the solder connection. :)
Interesting take on a MOSFET driver using PC817 optoisolators. IIRC most power transistor drivers that I see and work with in AC drives, inverters and power supplies use a _HCPL3120_ , _TLP250_ , or some varient of a high current optoisolator designed to drive high capacitive, high current gates of IGBTs and MOSFETs. Although in some applications I do see an IR2110 being used instead.
I don't think it'll matter at 31khz, but darlington opto-isolators are more sluggish than single transistor types. The ones I've salvaged have all been darlingtons and I couldn't get a nice 1mhz square wave through them (at 5V output). I might have put this comment on the original DCOI videos, so apologies if so.
Aaargh... totally expecting to see the scope in action... now desperately waiting for part 3... (Still a very interesting mini-series nonetheless. Thanks!)
Loving the muppet series! Have u thought about using the pic12f from your pic series instead of the arduino? Guessing you'd need more than one so timing could be a problem? Maybe a future upgrade.
Ideally a MOSFET should be driven by a roughly symmetrical bipolar voltage, ie it should be driven by say +15V to turn it on and -15V to turn it off (relative to the Source) with a current capability of about one amp. What really counts is the current that you put into and take out of the gate so it can be done with different voltages if the source impedances are adjusted accordingly but it's difficult to take enough current out of the gate if the gate driver voltage is zero relative to the gate. In high frequency switch mode converter design it's all about driving the MOSFETs on and off fast enough. It's no good trying to run a converter at say 100kHz ( period 10us, minimum on-time say 3us) if your switching delay is 5us. These opto couplers have rise and fall times of about 6us at 30mA.
A simple trick that we used to use before the days of dedicated MOSFET driver ICs was to use 4000 series CMOS buffers such as the CD4049 or the CD4050. We used to parallel them up to get lots of drive current with a rail-to-rail voltage swing. eg parallel up five buffers and use the sixth one to drive them giving a low input capacitance to the source. For high side switches we used transformer coupling with capacitor coupled connections to the gate to provide a bipolar drive voltage. This of course doesn't allow the duty cycle to go to zero or 100%. The amount of drive current you need depends on how big the MOSFET is we were always trying to drive big FETs at tens or hundreds of watts.
5v - (1.2 + 1.8) / 150 ~= 13mA driving the opto. Ic to the gate is only 10-20mA at best at 9V. A higher voltage or better CTR opto would improve the Mosfet turn on time. I tend to find a way to use the 4N32 darlington because I have a stick full of them as well ;)
IIRC, there are DC-DC converters that are completely isolated from input to output, I only remember seeing 5V versions but perhaps there's 9V or even 12V versions? Worth looking into so you don't have to rely on that 9V battery :)
Member Berry not sure about DE but the wife here in US had a good sized pack of Fun-Tak which seems like the same thing, and thanks the Julian, I have been using it quite a bit for helping hands and temporary mounting.
Why is the pwm frequency so high at 31khz?what's the advantage of a higher or lower pwm switching rate?I know DC motor controllers for EV's normally run about 20khz but I've never understood why so high
Higher switching rates allow the use of smaller inductors inside the H-bridge, smaller smoothing capacitors for the output voltage, and generally faster control.
You want to go above 20 kHz to avoid the irritating sound. Otherwise it is a compromise. A higher frequency gives higher switching losses in the power semiconductors but also makes it possible to use smaller/lighter inductive components.
Hi Julian. Really nice work. I intend to make my own DCOI using EL817 from Mouser. Can you describe the specs of your sharp opto-coupler or otherwise check the specs of mine to ascertain that it would work.
maybe you should measure the leakage through transistors because leds have very small leakage so that gets amplified by transistors and cause higher current maybe I am not sure about that.
It looks just like the component tester I've used in my latest video upload (for something totally different). That one is marked GM328A V1.11. I bought it via AliExpress. On the back it is labeled Electronics studio and it features the Atmel ATmega328P MCU.
Hello julian Would you not even(For a moment) want to look at the CW decoder? Morse decode with an Arduino? There is quite a lot on the internet but it is (I think!) All still pretty blurred! How you make it and how about the software. With two (2) rows of LCD or and with four (4) row of LCDs Transmit only or Transmit an receive I think that this issue is still unclear! Hereby I also give you a link from an SW recipient: Http://websdr.ewi.utwente.nl:8901/ Receiver If you clicked the link you must still set the SDR. The SDR does it but it is still unclear on the screen! Set it up first! If you manage to get a bit of a tunner then turn on CW - And search between the 14000kHz and the 14050kHz The recipient can still MUCH more! Also take a look around if you want. Next time if you like it I'll tell you more! friendly greetings from The Netherlands! Rob.
I really wouldn't recommend relying on the solder to hold the MOSFET to the 2-pin header; just stick the MOSFET pins directly into the machined-pin sockets. Or solder some short lengths of stranded hook-up wire between the MOSFET and the 2-pin header; let the wire flex, rather than the solder connection. :)
This kind of educational videos are the reason I subscribed. I'm very happy to see them again :)
Thanks Telmo, I appreciate your interest :)
Should I be laughing at someone looking for their glass's ?
Interesting take on a MOSFET driver using PC817 optoisolators. IIRC most power transistor drivers that I see and work with in AC drives, inverters and power supplies use a _HCPL3120_ , _TLP250_ , or some varient of a high current optoisolator designed to drive high capacitive, high current gates of IGBTs and MOSFETs. Although in some applications I do see an IR2110 being used instead.
I don't think it'll matter at 31khz, but darlington opto-isolators are more sluggish than single transistor types. The ones I've salvaged have all been darlingtons and I couldn't get a nice 1mhz square wave through them (at 5V output). I might have put this comment on the original DCOI videos, so apologies if so.
Aaargh... totally expecting to see the scope in action... now desperately waiting for part 3...
(Still a very interesting mini-series nonetheless. Thanks!)
The newer firmware for the GM328A will read Rds as well.
Loving the muppet series!
Have u thought about using the pic12f from your pic series instead of the arduino?
Guessing you'd need more than one so timing could be a problem? Maybe a future upgrade.
Ideally a MOSFET should be driven by a roughly symmetrical bipolar voltage, ie it should be driven by say +15V to turn it on and -15V to turn it off (relative to the Source) with a current capability of about one amp. What really counts is the current that you put into and take out of the gate so it can be done with different voltages if the source impedances are adjusted accordingly but it's difficult to take enough current out of the gate if the gate driver voltage is zero relative to the gate. In high frequency switch mode converter design it's all about driving the MOSFETs on and off fast enough. It's no good trying to run a converter at say 100kHz ( period 10us, minimum on-time say 3us) if your switching delay is 5us. These opto couplers have rise and fall times of about 6us at 30mA.
number 33 keen to have your alternative if you have a nice quick one you can recommend for higher frequencies
A simple trick that we used to use before the days of dedicated MOSFET driver ICs was to use 4000 series CMOS buffers such as the CD4049 or the CD4050. We used to parallel them up to get lots of drive current with a rail-to-rail voltage swing. eg parallel up five buffers and use the sixth one to drive them giving a low input capacitance to the source. For high side switches we used transformer coupling with capacitor coupled connections to the gate to provide a bipolar drive voltage. This of course doesn't allow the duty cycle to go to zero or 100%. The amount of drive current you need depends on how big the MOSFET is we were always trying to drive big FETs at tens or hundreds of watts.
Do you use the antix tips from maplin or do you use a tip form a different make, shop etc?
@2:09 I always break off my middle leg before checking my capacitance.
This presentation was sponsored by Blu Tack.......
Hi julian, ive got a 29v (out put )battery i just made. Its not balanced, what voltage should i use to charge it.
5v - (1.2 + 1.8) / 150 ~= 13mA driving the opto. Ic to the gate is only 10-20mA at best at 9V. A higher voltage or better CTR opto would improve the Mosfet turn on time. I tend to find a way to use the 4N32 darlington because I have a stick full of them as well ;)
IIRC, there are DC-DC converters that are completely isolated from input to output, I only remember seeing 5V versions but perhaps there's 9V or even 12V versions? Worth looking into so you don't have to rely on that 9V battery :)
+Skruffles You must have read my mind ;)
Can't you use the either the solar input or the battery output in the finished circuit?
It doesn't need regulating AFAICS, as long as it's high enough voltage to turn the mosfet on. A local decoupling cap never hurts of course.
Where did you get that bluetac? I cant find it in the Shops here in Germany :(
IRL Shops? Well, guess the internet is a much better place, e.g. search on Amazon Germany for B00I42EOJE. :o)
Member Berry not sure about DE but the wife here in US had a good sized pack of Fun-Tak which seems like the same thing, and thanks the Julian, I have been using it quite a bit for helping hands and temporary mounting.
Why is the pwm frequency so high at 31khz?what's the advantage of a higher or lower pwm switching rate?I know DC motor controllers for EV's normally run about 20khz but I've never understood why so high
Higher switching rates allow the use of smaller inductors inside the H-bridge, smaller smoothing capacitors for the output voltage, and generally faster control.
You want to go above 20 kHz to avoid the irritating sound. Otherwise it is a compromise. A higher frequency gives higher switching losses in the power semiconductors but also makes it possible to use smaller/lighter inductive components.
Hi Julian. Really nice work. I intend to make my own DCOI using EL817 from Mouser. Can you describe the specs of your sharp opto-coupler or otherwise check the specs of mine to ascertain that it would work.
PC817 and EL817 are the same
Thanks Julian. I shall find another part and will share with you my experience.
maybe you should measure the leakage through transistors because leds have very small leakage so that gets amplified by transistors and cause higher current maybe I am not sure about that.
which component tester is that you are using? Thanks
It looks just like the component tester I've used in my latest video upload (for something totally different). That one is marked GM328A V1.11. I bought it via AliExpress. On the back it is labeled Electronics studio and it features the Atmel ATmega328P MCU.
Maxint R&D Thanks
Maxint R&D f
Okay that is pretty cool.
Could anyone say me about muppet 2 project in simple english.....?
Eden's Aquaponics Ah......I see.....So what is he trying to do ?
So essentially this will be solar panel driver?
Pavel Shlapak Yes
Pavel Shlapak Ah......Now I get the MUPPET thing.......
Is this circuit also working with an input voltage of 3,3 volts?
+Kirian F It's 5v only. Lots more videos on my channel on DCOI.
Hello julian
Would you not even(For a moment) want to look at the CW decoder?
Morse decode with an Arduino?
There is quite a lot on the internet but it is (I think!) All still pretty blurred!
How you make it and how about the software.
With two (2) rows of LCD or and with four (4) row of LCDs
Transmit only or Transmit an receive
I think that this issue is still unclear!
Hereby I also give you a link from an SW recipient:
Http://websdr.ewi.utwente.nl:8901/
Receiver
If you clicked the link you must still set the SDR.
The SDR does it but it is still unclear on the screen!
Set it up first!
If you manage to get a bit of a tunner then turn on CW -
And search between the 14000kHz and the 14050kHz
The recipient can still MUCH more! Also take a look around if you want.
Next time if you like it I'll tell you more!
friendly greetings from The Netherlands!
Rob.
dcoi spends so much current through leds. how about using IRLZ44N ?
Second