My silly voltage multiplier only works if I ground it

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Hi Pix
A circuit would help.
Also what sort of diode are you using. A 1N400X will be no good. Only looks like a piece of wire when the frequency gets much above 100Hz.
Cheers Bob

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Sure thing. Ill put the part numbers and values on there too.

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Hi Pix
Where is your diagram
By “circuit” I meant a schematic type diagram, not a frizzing thing or a photo, and yes with component values etc.
Cheers Bob

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Ah sorry. I was going to attempt it in my lunch break but there was some vip customers that needed my attention more. Some days are chill and others are… not.

Im leaving work in an hour. Ill nail it out on the train on the way home. Excited to get your feedback. I always learn a lot.
Pix :heavy_heart_exclamation:

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Hi Pix
Sorry didn’t realise you are working. Get a bit used to thinking everyone is like me. Old and past it.
Cheers Bob

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No worries :smile:.
Im so stoked that your willing to help me Bob.
Thankyou.

I did my best to read the models on the diodes.
1n4799a
1n4934

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Hi Pix
Some pin numbers on the 555 would be a big help. I can guess most of it but like to be sure.
The 2 diodes in the pic are not the same, they should be fast types NOT the 1N400X series.
Your video says 22pF. your circuit says 22nF. Which is it. That is a difference of 1000 times, pretty significant.
I think the 4.4V you are measuring is the 5V minus the diode drops.
I think you are trying to rectify the 555 output and add it to the 5V.
I don’t think that could work. The diode anode currently connected to 5V should have the anode connected to ground.
This is a basic voltage doubler circuit which must have an AC input. That is the input swings + and - WRT to ground. To work this has to charge the first capacitor via the grounded diode when the input swings negative WRT ground. The 555 output does not do this. it only goes positive WRT ground and never goes negative so that first cap never charges.

The DMM input has an input resistance of 10MΩ which is quite high and what you are seeing when you put your finger anywhere could be anything. Try it, just grab the probe with your fingers and see what you get. An Oscilloscope would be useful here.
By the way, 5V is getting down to the lower limit for the 555 so that may have an influence with your fingers. They are happier with a few more volts. I think there is a lower voltage version these days but am not sure.
Cheers Bob

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Hi Pix
Just found the circuit you are using. It and an explanation found here

This should produce a voltage double minus 2 diode drops but with very little current capability. The diodes are all important. Find some schottky devices or go down to Jaycar and get some 1N5919. Also where have you got that LED connected. This could be fouling things up a bit, after all it is basically a diode. I won’t have time for a few days but I might build that up and see what is going on. Make up your mind re those 22 ?? caps though.
Cheers Bob

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Thanks Bob :grin:

I’ve replaced the diagram on my last post with an update. :slight_smile:

I still haven’t figured out how to measure capacitance with my multimeter (if it’s possible at all).
Having done some online research I’ve become pretty convinced that it’s pico-farads.
Here is a photo of the capacitor for clarity.
I’ve added that correction to the diagram as well.

This is so much better than the videos and articles I’ve been following.
Great find.

Gotcha! As a learning opportunity, what is the difference between this diode and what I’m using?

The anode of the LED is connected to pin 3 of the NE555. It’s just visualizing the oscillation. Not sure if this is relevant but I grounded the cathode of the LED via a 220ohm resistor.

You’re the best!
Pix :heavy_heart_exclamation:

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The following is from a project by student. It is well documented and explains everything.

Another project write up.

Tutorial on using 555 timer.
https://www.electronics-tutorials.ws/waveforms/555-circuits-part-2.html

The two projects use capacitors in the microfarad range which makes more sense to me than the picofarad range.
They use 1N4007 diodes. In your video you say, “zenner diode”. Don’t think it will work with a zenner diode.

There is a wiring discrepancy in the second project. Pin 2 of the 555 and pin 6 should be connected for oscillator operation. (typo maybe)

Anyway, hope this helps.
Cheers
Jim

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HI pix
Apologies. When I started to insert 555 pin numbers i realised the sketch was a pic of the timer itself.

Pin 4 should be connected to pin 8. Not left floating.

About a 10nF cap from pin 5 to ground would not hurt.

I don’t know what your diodes are but as your frequency seems to be approx 100Hz any of the 1N400X (1N4002, 4, 7) will do. any frequency above that you will probably need schottky diodes such as the 1N5819 (not 5919 as i incorrectly posted). The schottky diodes have a lower forward voltage drop so you would get a little closer to 10V than with the 1N400X series.

The 22 on that cap does not indicate what the multiplier is so would need to be measured, can do with some multimeters but maybe not with the cheap ones. It does not appear to be ceramic so maybe is 22nF. Anyway this is far too low. I would suggest 22µF or even 220µF. I think preferably low ESR types.

The 555 does not have a large current capability so to minimise the LED influence increase the resistor value to say 330, 470 or even 1k. It is just an indication so does not have to be very bright.

As a matter of interest what are you going to use 10V for. You won’t have much current capability so it will really only be a voltage source. A charge pump is needed to use an N channel Mosfet as a high side switch (instead of the more common P channel) or some motor drive circuits use an N channel Mosfet as a flywheel diode. Also some H bridge ICs have this built in to switch the high side bridge devices.

It would also do you some good to look as James’ links

I did not pick up on your use of “zener” diode in your video. James is quite right. It probably would not work. Would depend on what the zener voltage is.
Note his reference to pins 2 and 6 being connected. They must be. You have shown them connected correctly in your sketch.
Cheers Bob

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Diodes

Worth a shot, I’ll go pick some up.

I’ll get some of these too. They’re cheap and I’m sure I’ll find a use for them eventually.

Caps

I’ll try some other capacitors. I have some nice ceramic caps that might work :slight_smile:

the why of this whole thing!?

This is a proof of concept.
Eventually I want to double a 9v battery and get 18v 100ma.
I’m sure I’ll have to make some modification when I get there.
For my first attempt, I ran on 5v. Ended up being a good call.

LED

I like this idea.

Tutorial

That was a great read, Thanks @James46717

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Hi Pix

I don’t think they will be large enough value. They are probably in the pF or low nF range. You need to get into the µF ranges. Low ESR electrolytic.

Re 1N4007. They have an inverse voltage rating of 1000V. You don’t need anything like this. !N 4001, 4002, 4004 will do. The inverse rating for these is 100V, 200V and 400V as suggested in the type number.

I think you need to read up a bit on the different types of components like capacitors, resistors, diodes etc and get an idea about what each different type is used for and how used. For instance most electrolytic have far too much inductance to be effective at high frequencies so you will often see say a 470µF or 1000µF electrolytic bypassed with a 10n or 100n cap to bypass any high frequency component while the electrolytic smooths out DC. Especially on power supply outputs.
Cheers Bob

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I just got these because it’s what they used in the tutorial linked by james Is there any reason a 1n4004 would be superior?

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Hi Pix

NO. The only difference is the inverse voltage rating. They all have the same current rating (1A). A lot of people (myself included) tend to keep a supply of these as they can be used almost anywhere without having to worry about voltage ratings. Probably a relic habit from the old high voltage (300 plus) days. The only con would be the forward voltage drop which could be as high as 0.7V. All models are the same in this context.

The only comment I would make regarding the diodes used in that link is the 555 is operating at a quoted 2kHz which is I think getting into the stage where these devices (being power rectifiers) are ceasing to be an effective diode. A bit border line I think and I personally would be using schottkys or other high speed devices here.
Cheers Bob
PS I was a bit wrong re reverse voltage rating. Here is the extract from latest data sheet.


For interest only. Does not affect you in any way. Note the forward voltage drop is quoted at 1V which you will need to subtract 2V from whatever you expect the output to be.

As a comparison

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See circuit below.
In the video you say 0.33uF so included the frequency it would produce.
Both the project links state 2KHz which I think is incorrect, using the values I calculate about 200Hz.
Using the formulae in the tutorial link.

I listed 1N4002, it could be any in that range.
Or the schottky diode @Robert93820 mentioned to reduce the voltage drop across the it.

The output capacitor needs to be in the uF range to compensate for current drain.
The charge on a pF or nF capacitor is pretty small.
It is probably why you were seeing it change when touching it.

When you come to doing the 9V to 18V you will need to add a transistor or mosfet to get the 100mA.
The 555 cannot output that much current and you may need much larger capacitors.
The 470uF should be good for a few mA.

Regards
Jim

image

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Hi All.
Just to get a little academic.
Below is a scan of a page from the publication “IC Timer Cookbook” by Walter G. Jung which is I think considered something of a bible on the subject. My copy is the 4th printing 1981 and is pretty well falling apart but I treat it with loving care.

Plugging the values in Pix’s circuit I come up with the following frequencies.
For “C” = 1µF f ≈ 101Hz
For “C” = 0.33µF f ≈ 307Hz

James is correct here. I plugged in the values in the second link and came up with ≈189Hz. Don’t know where the 2K came from. Both links use the same values for the 555. Could have got the decimal point in the wrong place, easily done and that would do it.

For your information Pix. All values have to be in the same units. That is F = Farads, R = Ohms OR F = MicroFarads and R = Megohms. And “f” will be Hz
Cheers Bob

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:partying_face: :partying_face: :partying_face: :partying_face: Success! :partying_face: :partying_face: :partying_face: :partying_face:


The answer was a combination of larger capacitors and 1n4004 diodes.
It’s not double, but I’m hopeful it’s adequate for my needs.
Thanks @Robert93820 and @James46717 for all your help.

I’d like to measure the amperage of this circuit with my multi-meter.
My understanding is that I want to put my probes in series with the circuit.
At first i put my probes in parralell. The LED shut off and the diodes got quite hot.
I got a reading of nearly 1A. See a pitcture below with a plus and minus for where I placed the multimeter probes.

:man_facepalming:

Ok, mistakes were made. No matter.
Here is the meter in series.
Now I’m showing zero… that seems too small given that the led is on.

What is a better, safer way of measuring amps on this circuit?

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A meter in current mode is a dead short, so the 1A you saw was limited by the components in the circuit. So that’s the maximum the circuit could supply, though likely not for very long. What you need to know is the current that is required for your load. To measure this put the meter in series with the supply to the load. If that is anywhere near 1A then the circuit is not adequate for the task.

Always turn your meter back to voltage or resistance after using the current mode in order to avoid damaging something the next time you use it.

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