I was wondering as well weither a current-limiting resistor was necessary (on both chip pins actually: +3V and clock). Driving a 1uF cap straight from a pin definitely gets me anxious.
You aren't really driving a capacitive load though, you are just changing the reference voltage. Nearly all of the energy in the system is going to come from the VCC pin in the circuit that charges the cap once your clock pin goes low and the cap voltage is lower than VCC.
You definitely should! First try to understand how it works. Then you see why it's always good to have a bunch of them lying around in the parts drawer. Just yesterday I needed a square wave with variable frequency (from .1 to 1kHz) to flash some LEDs. If you're fine with fixed 50% duty cycle, search for "mini-astable ne555". A NE555, one resistor and two caps, that's it. It's also a circuit I like, because it's "unusual", in that it uses the output pin itself for the timing.
Thank you! This tutorial is nine years old so you may never see my comment. I couldn't get my circuit to work until I saw your tutorial and built your circuit.
Dear good sir, I'm so lucky that I found your channel. Now I can use this method for my capstone project! Thank you so much. I love your teaching. So easy to understand the theory. It helps alot when you do the exxperiment right after.
Used as a source, the current to the load is coming from the capacitor charged up to 3V, which charges the grounded capacitor up to 6V thanks to that boosting effect. The cap gets re-charged (to at most 3V) when PWM = low, and THAT current comes from point 1; when PWM = high, the diode blocks reverse current from cap to point 1. There shouldn't be a point where both cap terminals are 3V once the thing's running, unless your load is so big that the cap gets fully discharged.
I think what you're missing is that a charged capacitor maintains the voltage across itself (ΔV_C) as long as no current passes through it (incl. leakage). Furthermore, ΔV_C(t) is always continuous. Look at the circuit when PWM = 0V. Point 1 is 3V_{DC}, so the capacitor can charge to 3V. Later the PWM voltage = cap bottom lead voltage = 3V, and the capacitor maintains ΔV_C = 3V it charged up earlier; the voltage at the top lead is therefore 3V + ΔV_C = 6V (with reference to ground).
thanks Dave, this is exactly what I was looking for to work around some issues with a project I'm totally new to electronics - and your vlog has helped me in a lot of ways
When the PWM goes high, you are lifting the "ground" of the cap to +3v. This lifts point 1 to +6v through the cap. The current comes from the charge stored across the cap.
What I like most about his videos are: He removes empty parts of video, like while he is writing something to board; I mean at 4:58 no graph - at 4:59 colorful graph plotted and his speech goes like there is no video edit, magic happened,
Wow amazing, I went to school for computer engineering years ago and I came across this video. You're amazing btw, but this video gave me so much nostalgia! I miss working on EE stuff.
Depends on the uC and the load but e.g. Atmega328 provides 40mA and similar uCs provide similar current I guess. The MSP430g2253 for example provides 20mA max current per pin. Furthermore you have to drive the driver as well ;)
Wouldn't you want a current-limiting resistor or something on the PWM output? Otherwise it seems the instantaneous current would exceed the microcontroller's absolute maximum rating.
If anyone's wondering what the name at 1:21 actually is here's the reference Greinacher circuit in en.wikipedia.org/wiki/Voltage_doubler#Greinacher_circuit
What about the inrush current exceeding the maximum output current of the micro? At start up the output pin will be effectively shorted to ground through a diode.
I want to ask two things: First is that voltage dropped mostly on diodes , maybeyou can use MOSFET instead of diode? Maybe more power efficient also. Another concern, imho when you drive capacitive load, it increases requirements to capacitor on microcontroller power circuit, because on battery powered setup initial stage of capacitor charge will draw relatively significant current, and will cause also significant supply voltage drop (which will lead to supervisor shutdown, or glitches)
The ansewer is weared by dave... it's called ne555 (you can use the magic ne555 in astable mode) :) or you can use the pwm module on pic. Everythigs than generate an oscillating signal can work. (sorry for my english :) )
A method to increase the power of this kind of charge pump is to multi-phase interleave them, I got a 3-phase voltage inverter charge pump in my product and it just works fine, transformer eliminated!
from those i have, the one with the highest reverse current is the mur820(8A 650mV Vf) with 5µA and the one with the lowest is the bat85 (200mA 240mV Vf) with 500nA. Compared to the nothing special 1n4148 (200mA 500mV Vf) with 7nA (all at 25V 25ºC, Imax Vf min), yeah that's a lot but still dont think that's gonna affect the doubler in any way except for the higher voltage due to less losses on the diodes. Not sure about those with miliamps of Ir but maybe those were the old ones?
Could you use 2 transistor astable multivibrator to provide the signal for the multiplier? What frequency should it resonate in? Also if the same one multivibrator was at the end of this, providing 9V pulses to this circuit and a piezo buzzer would it work?
What I don't understand is the PWM is 3V with reference to ground, point 1 is 3V to ground. So across the first cap coming from the PWM is 3V and 3V so where is the current coming from?
Prefer these over tear downs from a learning perspective - wish you did more I'm interested in how you'd handle 3.3v to 5v for ttl serial interfacing (extending on this video topic)
Thankd dave...very Educative. I actually had an issue with a low dc voltage in my latest design..this will surely help out. I was thinking....do you have any video on how to perfectly use Oscilloscopes, especially when powered by AC mains...to avoid damaging your circuits by a blast..tnks
I would really like to see you read the AC Line frequency vs a RTC or your rubidium clock with a micro-controller! That would be very interesting to see....
Most of the pic micros, can sink only 20 mA, on the entire port i think. So whether we need a current limitting resistors. Or do we need to sdjust the fz, and there by increasing the importance to reduce the current?
As usual, kudos on a job well done! I have been simulating your circuits using EasyCircuit and was surprised that a) your circuits really do as you say, and b) that EasyCircuit results are very accurate. Also, at the end of most of your videos I find myself thinking (using a chipmunk voice) gee Dave!
Dave, can I power it from a sine RF signal of say 15MHz, or does it need to be a square wave? I would like to use this as a DC-DC doubler for feeding a 14V varicap from 12v. I choose 15MHz so that the second harmonic is just above the HF (30MHz) to avoid interference to my RF circuit.
lol that gets crazy... in lab at university it took 2 months just to learn how to use the software and its design rule checks to build a simple bandpass filter.. fyi you can do the same filter i did on that chip with only a few resistors, caps and transistors
I wonder if the switching input from the microcontroller is drawing too much current for a tiny uC. Would be better to put a kind of driver (MOSFET?) on this line?
hey dave how about explaining joule thieves next? to continue white the voltage multipliers/converters idea. Also really useful what you dont have a clock signal or a really low voltage source like a single 1,5v AAA
There seems to be some ghosting or screen burn in the lower left hand corner of your DaveCAD screen there - should have used an amusing screensaver....
Very nice video, reminds me of using the XOUT pin of a PIC16C711 in1994 for generating -4V for an OPAMP. Still thinking if i should have tried harder finding a real RRIO opamp, since my input voltages were only down to 0V, hehe. Oh please don't point out RRIO OPAMPs to me available in 1994 :P
Hi Dave just trying to replicate your circuit. At 24min you say oops wrong polarity. Does that mean I should be using a negative signal. I was under the impression from the beginning that it was a positive signal inducing a negative charge on the capacitor? I am using a SSR 40d as my signal so I can do either. Any help appreciated Thanks Raef
Hi Dave, great tutorial. Question, how do did you connect the voltage multiplier to your o-scope? The doubler does not appear to have one common ground reference and it does not look like you used differential probes. Thanks!
+Sanjay Verma good remark you'll kill your mcu ?! i've try some sim on ltspice; i don't think a 16f or 18f is able to survive it ^^(100ohm load 5v input , 12v output, you need something like 800mA) but it work for 1-10kohm load ( like a vfd where you need 15v-25v for a very litle current (can't measure it with my multimeter)) or you can use some mosfet, i guess that's always the problem with these explanation where you use some simplification let's say it's good to make money and to have suscriber
22:35 why does the voltage of the second stage drop below both the earlier (first) and layer (third and fourth) stages? Anyone with better EE understanding want to tell me? Could a modified common ground circuit here (that aligns the phase of each stage's ground) "recycle" some of the wasted energy here (and put it back to the load)(perhaps put an inductor in the virtual ground, or some kind of shunt)? Thanks all!
Can you drives circuit like this from a 3V3 microcontroller that has 12 VDC rails available (to get 24 VDC)? I assume you just replace the direct pin connection a “2” with a MOSFET.
Why the ripple is getting bigger along with the load? I predict it has something to do with discharging the capacitor, but could someone explain it precisely?
Dear Dave, I love your blog :) Would you like to make a video that describes the difference between tantalum, mlccs, electrolytic, etc. caps related to frequency? would be nice! Greets from Austria, not Australia ;)
yeah but theres more to it though..tantalums have leakeage asociated with them..mlcc loose their capacitance with applied voltage and ers dependent on temp and freq..(refer to kemet spice) that video gives a very surface level breakdown
By far my favorite, and in my opinion the most informative EE, youtuber. Very good video as usual
Micro controller spec sheets warn against driving capacitive loads, so buffering the io pin may be required. Great video mate! Thanks.
I was wondering as well weither a current-limiting resistor was necessary (on both chip pins actually: +3V and clock). Driving a 1uF cap straight from a pin definitely gets me anxious.
You aren't really driving a capacitive load though, you are just changing the reference voltage. Nearly all of the energy in the system is going to come from the VCC pin in the circuit that charges the cap once your clock pin goes low and the cap voltage is lower than VCC.
@@AustinSteingrube What is VCC, is it stand for voltage charging circuit?
@@ryanb1874 "VCC" stands for "Common Collector Voltage". It is basically just your positive voltage supply. Nothing fancy.
@@AustinSteingrube is there really a difference between positive, and negative voltage, material, or like affecting, electron migration?
Great video, even after 9 years!
You definitely should! First try to understand how it works. Then you see why it's always good to have a bunch of them lying around in the parts drawer. Just yesterday I needed a square wave with variable frequency (from .1 to 1kHz) to flash some LEDs. If you're fine with fixed 50% duty cycle, search for "mini-astable ne555". A NE555, one resistor and two caps, that's it. It's also a circuit I like, because it's "unusual", in that it uses the output pin itself for the timing.
Thank you! This tutorial is nine years old so you may never see my comment. I couldn't get my circuit to work until I saw your tutorial and built your circuit.
Dear good sir, I'm so lucky that I found your channel. Now I can use this method for my capstone project! Thank you so much. I love your teaching. So easy to understand the theory. It helps alot when you do the exxperiment right after.
Used as a source, the current to the load is coming from the capacitor charged up to 3V, which charges the grounded capacitor up to 6V thanks to that boosting effect. The cap gets re-charged (to at most 3V) when PWM = low, and THAT current comes from point 1; when PWM = high, the diode blocks reverse current from cap to point 1.
There shouldn't be a point where both cap terminals are 3V once the thing's running, unless your load is so big that the cap gets fully discharged.
I think what you're missing is that a charged capacitor maintains the voltage across itself (ΔV_C) as long as no current passes through it (incl. leakage). Furthermore, ΔV_C(t) is always continuous.
Look at the circuit when PWM = 0V. Point 1 is 3V_{DC}, so the capacitor can charge to 3V.
Later the PWM voltage = cap bottom lead voltage = 3V, and the capacitor maintains ΔV_C = 3V it charged up earlier; the voltage at the top lead is therefore 3V + ΔV_C = 6V (with reference to ground).
thanks Dave, this is exactly what I was looking for to work around some issues with a project
I'm totally new to electronics - and your vlog has helped me in a lot of ways
When the PWM goes high, you are lifting the "ground" of the cap to +3v. This lifts point 1 to +6v through the cap. The current comes from the charge stored across the cap.
This is awesome. Done this a while ago on a project but good to see the application again. :)
What I like most about his videos are: He removes empty parts of video, like while he is writing something to board; I mean at 4:58 no graph - at 4:59 colorful graph plotted and his speech goes like there is no video edit, magic happened,
I love this series. I am learning so much from this videos. Thank you!
Excellent video. Although I've built it in the past already I like the video very much and please, keep those tutorials/lectures comming.
Wow amazing, I went to school for computer engineering years ago and I came across this video. You're amazing btw, but this video gave me so much nostalgia! I miss working on EE stuff.
Why didn't you use dual diodes on the watch to save space?
Oh, and you forgot to mention you can use this method to generate negative supplies...!
I used a charge pump to create a negative rail for a couple of my projects (which worked a treat). Maybe you should give that a mention some day.
Depends on the uC and the load but e.g. Atmega328 provides 40mA and similar uCs provide similar current I guess. The MSP430g2253 for example provides 20mA max current per pin. Furthermore you have to drive the driver as well ;)
Hey that is my registered key for DaveCAD!!!
Now I'll have to buy another license....
Another great vid Dave!
Wow, this is very good. Did not know you could do a pump stage like that.
Thanks.
Always very helpful, thank you Dave, it' s a pleasure to watch your video
Hi mate,I think that your videos are brilliant & very informative as always & i have learned a fair amount from them .Keep up the good work,cheers.
Thank you Dave. This helps me a few times.
fantastic video! Fashion show, audio at the end, never know what'll happen next. Content is great. Love it!
Its also worth saying that negative voltages can be generated by inverting the circuit
I did a quick google and I found values ranging from 20 microamps to 1 milliamp, so if you shop around it shouldn't be a problem.
Wouldn't you want a current-limiting resistor or something on the PWM output? Otherwise it seems the instantaneous current would exceed the microcontroller's absolute maximum rating.
If anyone's wondering what the name at 1:21 actually is here's the reference Greinacher circuit
in en.wikipedia.org/wiki/Voltage_doubler#Greinacher_circuit
What about the inrush current exceeding the maximum output current of the micro? At start up the output pin will be effectively shorted to ground through a diode.
This is my favorite series from you right now, keep it goin
Love the war games quote at the end. Great job as always Dave
A brilliance derived by brilliants.
I want to ask two things:
First is that voltage dropped mostly on diodes , maybeyou can use MOSFET instead of diode? Maybe more power efficient also.
Another concern, imho when you drive capacitive load, it increases requirements to capacitor on microcontroller power circuit, because on battery powered setup initial stage of capacitor charge will draw relatively significant current, and will cause also significant supply voltage drop (which will lead to supervisor shutdown, or glitches)
The ansewer is weared by dave... it's called ne555 (you can use the magic ne555 in astable mode) :) or you can use the pwm module on pic. Everythigs than generate an oscillating signal can work. (sorry for my english :) )
A method to increase the power of this kind of charge pump is to multi-phase interleave them, I got a 3-phase voltage inverter charge pump in my product and it just works fine, transformer eliminated!
13:13 got me with the license popup there!
from those i have, the one with the highest reverse current is the mur820(8A 650mV Vf) with 5µA and the one with the lowest is the bat85 (200mA 240mV Vf) with 500nA. Compared to the nothing special 1n4148 (200mA 500mV Vf) with 7nA (all at 25V 25ºC, Imax Vf min), yeah that's a lot but still dont think that's gonna affect the doubler in any way except for the higher voltage due to less losses on the diodes. Not sure about those with miliamps of Ir but maybe those were the old ones?
What simple passive circuit would push the waveform into the positive range while halving or dividing the p-p voltage?
Could you use 2 transistor astable multivibrator to provide the signal for the multiplier? What frequency should it resonate in?
Also if the same one multivibrator was at the end of this, providing 9V pulses to this circuit and a piezo buzzer would it work?
Thank you for this very educational video.
Hi Dave, I love your fundamentals friday. Greetings from Germany.
Loving this series Dave! Always fun and interesting. Keep up the good work!
I have a Communications Electronics Exam in 2 hrs :( Please guys wish me luck ! .. Dave ,, you are so greaaat !
Also looks like a great way for me to generate a higher voltage to switch on my N-Channel high side MOSFETs...
I don't really see a problem with the exposure.
What I don't understand is the PWM is 3V with reference to ground, point 1 is 3V to ground. So across the first cap coming from the PWM is 3V and 3V so where is the current coming from?
Prefer these over tear downs from a learning perspective - wish you did more
I'm interested in how you'd handle 3.3v to 5v for ttl serial interfacing (extending on this video topic)
ASMR circuit explanations is what that is.
Thankd dave...very Educative. I actually had an issue with a low dc voltage in my latest design..this will surely help out.
I was thinking....do you have any video on how to perfectly use Oscilloscopes, especially when powered by AC mains...to avoid damaging your circuits by a blast..tnks
I would really like to see you read the AC Line frequency vs a RTC or your rubidium clock with a micro-controller! That would be very interesting to see....
You can easily run a lcd from 3.3 V by giving it a negative contrast voltage (via such a chargepump) ;-)
Which is how 3V3 display modules are often built, with only the capacitors not glued to the glass .
Most of the pic micros, can sink only 20 mA, on the entire port i think. So whether we need a current limitting resistors. Or do we need to sdjust the fz, and there by increasing the importance to reduce the current?
you forgot to link the voltage doubler video in the description!
Please renew licence, Love it.....
As usual, kudos on a job well done! I have been simulating your circuits using EasyCircuit and was surprised that a) your circuits really do as you say, and b) that EasyCircuit results are very accurate. Also, at the end of most of your videos I find myself thinking (using a chipmunk voice) gee Dave!
Dave, can I power it from a sine RF signal of say 15MHz, or does it need to be a square wave? I would like to use this as a DC-DC doubler for feeding a 14V varicap from 12v. I choose 15MHz so that the second harmonic is just above the HF (30MHz) to avoid interference to my RF circuit.
lol that gets crazy... in lab at university it took 2 months just to learn how to use the software and its design rule checks to build a simple bandpass filter.. fyi you can do the same filter i did on that chip with only a few resistors, caps and transistors
The Analog Discovery is NOT a proper oscilloscope, not even close. It is not a replacement for a proper DS1052E.
How does the capacitor on the left charge. Is it from the +3VDC through the Capacitor and and back to ground via the signal generator ??
I want your T-shirt mate!!
Awesome video! I could have used this months ago during my school project. Lol.
I wonder if the switching input from the microcontroller is drawing too much current for a tiny uC. Would be better to put a kind of driver (MOSFET?) on this line?
Just what I need Dave here in 2024. Got a 3V supply and need 3V3 minimum for an LED.
would a fundamentals friday on decoupling caps be beneficial? is their enough information to cover for a video? if anyone could do it dave can! ;)
I see later in the video on the Agilent UI that you maybe used a dc offset of 1.5 to get the full 3. Is that in fact how you achieved the full 3V?
Great new series you started here, I like it a lot! (Though I hope the videos don´t get even longer...). Do you take suggestions for future topics?
"Please renew license" LOL
Google is your friend. Can be done so many ways. Using an opamp or an NE555 or inverters. The heck even the basic 2 transistor a-stable will do it.
i have no idea what the heck hes talking about, but i subscribed to him
12:30 Nice ad break. It could have used some cheesy music, though.
If you take the output back to the input, will the voltage keep escalating?
What's the best option to get 18V ~500mA from a 9V 1A power supply?
Could we use a 555 timer in a stable mode too create the square wave to drive this circuit ?.
A bright future in modelling me thinks.
hey dave how about explaining joule thieves next? to continue white the voltage multipliers/converters idea. Also really useful what you dont have a clock signal or a really low voltage source like a single 1,5v AAA
Excellent video - can you focus on microcontroller voltage inverter next time? How to make -5V from +5V?
There seems to be some ghosting or screen burn in the lower left hand corner of your DaveCAD screen there - should have used an amusing screensaver....
Very nice video, reminds me of using the XOUT pin of a PIC16C711 in1994 for generating -4V for an OPAMP. Still thinking if i should have tried harder finding a real RRIO opamp, since my input voltages were only down to 0V, hehe. Oh please don't point out RRIO OPAMPs to me available in 1994 :P
that shirt scene got me laughing me heart out lmao , i love you man.
Damn too clever for me. You really know your electronics.
Awesome electronics videos! Great work!
Hi Dave just trying to replicate your circuit. At 24min you say oops wrong polarity. Does that mean I should be using a negative signal. I was under the impression from the beginning that it was a positive signal inducing a negative charge on the capacitor? I am using a SSR 40d as my signal so I can do either.
Any help appreciated Thanks Raef
i don't see the link for the coch. walton voltage * vid that you mentioned in this vid, or whatever it is called. Just FYI
Could I take the doubled voltage and recenter it around 0 for a dual power supply +/-3v? That would be useful!
Just reverse the diodes and feed from ground, not +3V . No extra components and you can still use a 3 pin double diode package .
Another great tutorial!
Hey Dave!
Why can you use your standard 1N4007 diodes at 10 kHz ? Isn't the reverse recovery time too high for 10 kHz ?
Cockcroft-Walton multiplier, Dickson voltage doubler.. is it basically a prerequisite to have a name like that to name one of these things?
Hi EEVblog!
I would use 2 transistors, 1 PNP and 1 NPN for a Inverter Circuit. What do you think?
Hi Dave, great tutorial. Question, how do did you connect the voltage multiplier to your o-scope? The doubler does not appear to have one common ground reference and it does not look like you used differential probes. Thanks!
Have a play with the circuit. Both inputs and output do have a common gnd reference.
I see the light, thanks.
How would I make a voltage doubler for a 500mV input? What should clocks HIGH voltage be?
+Adriano Vianna Fonseca should match your dc input, so 500 mv also.
Well.... what if you used significantly larger capacitors and transistors to increase the current?... how much could we get?
So when you replaced the 0.47uF cap by a 47uF cap, you replaced the film cap by a electrolytic cap?
3 volt source has to deliver one half of the total load current and other half will be delivered by square wave source .......
+Sanjay Verma good remark
you'll kill your mcu ?! i've try some sim on ltspice;
i don't think a 16f or 18f is able to survive it ^^(100ohm load 5v input , 12v output, you need something like 800mA)
but it work for 1-10kohm load ( like a vfd where you need 15v-25v for a very litle current (can't measure it with my multimeter))
or you can use some mosfet, i guess
that's always the problem with these explanation where you use some
simplification
let's say it's good to make money and to have suscriber
22:35 why does the voltage of the second stage drop below both the earlier (first) and layer (third and fourth) stages?
Anyone with better EE understanding want to tell me?
Could a modified common ground circuit here (that aligns the phase of each stage's ground) "recycle" some of the wasted energy here (and put it back to the load)(perhaps put an inductor in the virtual ground, or some kind of shunt)?
Thanks all!
And Dave loves them
Can you drives circuit like this from a 3V3 microcontroller that has 12 VDC rails available (to get 24 VDC)? I assume you just replace the direct pin connection a “2” with a MOSFET.
Why the ripple is getting bigger along with the load? I predict it has something to do with discharging the capacitor, but could someone explain it precisely?
enjoyed the multiplier vids, have you done anything on the jewel thief circuit and how it works?
Big Clive is the Joule thief guy, he even created the name .
Dear Dave, I love your blog :) Would you like to make a video that describes the difference between tantalum, mlccs, electrolytic, etc. caps related to frequency? would be nice! Greets from Austria, not Australia ;)
yeah but theres more to it though..tantalums have leakeage asociated with them..mlcc loose their capacitance with applied voltage and ers dependent on temp and freq..(refer to kemet spice)
that video gives a very surface level breakdown