DC voltage booster not working as expected?

Thread Starter

Taymar

Joined Jan 13, 2017
31
Hi all, I'm pretty inexperienced with electronic circuits and would really appreciate any help in understanding the issue I'm seeing. I suspect it's due to a gap in my understanding of how this type of circuit works, but would like to confirm that it's not faulty hardware.

I have a 12v DC power source, that presently runs a couple of DC devices (wifi receiver, motor, LEDs). No issues there.

I now have a device (piezo atomizer) that requires 24v DC, and was hoping that I could run it from my same 12v source and use a voltage booster to get the required 24v.

This is the booster I bought:
https://www.amazon.com/gp/product/B00RXJJGE2/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

What I'm seeing though is unexpected. When I connect the voltage booster's input terminals to my power source, the voltage measured at the INPUT terminals is now 18v with no load. This is back feeding the source and meaning my other 12v circuits are also measuring 18v input, which is too high. No-load OUTPUT from the booster is measuring 24-25v at the same time.

When I connect my 24v device to the output of the booster, it works - definitely not as well as when it's powered by a true 24v, 700mA source (the power adapter it came with). My input voltage drops to around 9, and the output from the booster drops to around 15-18.

I think I understand in basic terms that the booster works by trading amps for volts.

My questions are:

1. Does this sound like my 12v power supply needs to be supplying more amps?
2. Is it expected that the booster would backfeed the INPUT with a higher voltage or does this sound like a defect? I don't want to let the magic smoke out of my 12v stuff. Would some kind of diode work here?

Thanks so much for any help. If there's a way to get this working without having to cave and run two power sources, that would be fantastic.
 

LowQCab

Joined Nov 6, 2012
743
You are probably seeing Voltage "Spikes" which may be created by the Inverter.
A big fat 1000uf, 35-Volt Capacitor will probably solve that.

You need to be thinking in terms of "Wattage" = Volts X Amps.
24-Volts X 0.7-Amps = 16.8-Watts,
is you current 12V Power-Supply capable of supplying 16.8-Watts, (plus additional losses) ?????
That would be roughly...... ~20-Watts -divided by- 12-Volts = 1.66-Amps.
So, can your current Power-Supply deliver 1.66-Amps while maintaining a solid 12-Volt Output ????
Evidently not .............
Your Power Supply should be able to easily supply roughly twice the Current that you need
for reliable, stable operation, meaning that,
You need a 12-Volt Supply that can deliver around ~3 to 4-Amps,
which is 4A X 12V = 48-Watts.

With the exception of the "Motor", (what ever that is),
Your other "normal Loads" are tiny by comparison, probably less than 250ma.
.
.
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Ohms Law FLAT .png
 

Thread Starter

Taymar

Joined Jan 13, 2017
31
Thank you - I've attempted to draw it here, please excuse the awful MS paint.

1. This is what my entire circuit setup would look like. 12v power supply outputs 12v to the Wifi/controller/motor stuff (that works totally fine without the booster in place).

I'd want to use the same power supply to ALSO run the booster, which in turn runs the piezo atomizer.

circuit-setup.jpg

2. This is the simplified test case I'm using - removed all my wifi/controller stuff so as not to risk damaging it until I get this figured out. The atomizer is connected to the output of the booster, and runs, but it's weaker than a 24v input. Connecting this drops the INPUT voltage down to 9v, and it's pulling about an amp. The output voltage is a bit higher and it's pulling only about 300ma.

2.jpg

3. If I remove the piezo atomizer and power on the circuit with no output load from the booster, the voltage measured at the INPUT now reads 18v - higher than the 12v source. If I had all my other stuff (wifi) connected here, presumably it'd be receiving 18v which is more than it's rated for.3.jpg
 

Thread Starter

Taymar

Joined Jan 13, 2017
31
You are probably seeing Voltage "Spikes" which may be created by the Inverter.
A big fat 1000uf, 35-Volt Capacitor will probably solve that.

You need to be thinking in terms of "Wattage" = Volts X Amps.
24-Volts X 0.7-Amps = 16.8-Watts,
is you current 12V Power-Supply capable of supplying 16.8-Watts, (plus additional losses) ?????
That would be roughly...... ~20-Watts -divided by- 12-Volts = 1.66-Amps.
So, can your current Power-Supply deliver 1.66-Amps while maintaining a solid 12-Volt Output ????
Evidently not .............
Your Power Supply should be able to easily supply roughly twice the Current that you need
for reliable, stable operation, meaning that,
You need a 12-Volt Supply that can deliver around ~3 to 4-Amps,
which is 4A X 12V = 48-Watts.
Thank you for this. I have a benchtop power supply that's capable of supplying that amperage, I will try it out. The PSU I'm using right now, I'm sure can't supply 3+ amps.

Where in the circuit would I put the capacitor please?

Would an underpowered PSU also explain the no-load input voltage jumping from 12 to 18v?

Thanks again, I will test with the big power supply and post back.
 

LowQCab

Joined Nov 6, 2012
743
If you want to try a Big-Capacitor, it should be as close to the Voltage-Boosting-Inverter as possible.
Make sure it's rated for at least ~24-Volts or more, or you could pop it, ( with a very loud POP ).

"" Would an underpowered PSU also explain the no-load input voltage
jumping from 12 to 18v? ""

My first guess is no.
But if Your 12V supply, and Your new 24V-Inverter, BOTH have inadequate Filter-Capacitors,
they could BOTH be contributing to that particular unusual problem.
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.
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Papabravo

Joined Feb 24, 2006
16,481
There is something very wrong going on here. A properly designed and fabricated DC-DC converter would not allow "backfeeding" as you put it. I'm not even sure that is a precise technical term. A cheap piece of poorly designed and manufactured crap from a 3rd world supplier could be doing almost anything. You do have to worry about the immutable rule of DC-DC conversion which is this:

The power out of a DC-DC converter will always be less than the power in. Sometimes it will be much less.

I suspect almost everything possible that could go wrong has in fact done so. Can you supply a link to the product that you purchased so we can try to determine if you should continue wasting your time with this. You can also work with isolated DC-DC converter, and they most certainly will not have any untoward behavior on the input regardless of what happens on the other side of the isolation barrier. For the time being we need to find an explanation for your observations.
 

Papabravo

Joined Feb 24, 2006
16,481
Here is the simplest and easiest to understand boost regulator model I have found. The diode D1, explicitly prevents "backfeeding" and is inherent in the design of the Boost Regulator topology. It would not be a boost regulator without it. Notice in the plot for the input voltage how "Rock Solid" it is. That is all in the diode,
 

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Papabravo

Joined Feb 24, 2006
16,481
So what is the procedure for setting the output voltage. Given the apparently wide input and output ranges, how is the device supposed to know what, precisely you want?

Tthis sentence from their ad is more than confusing to me, I can't really appreciate what it is talking about.
DC Boost Converter, Yeeco 150W 8A DC-DC Step Up Converter Board 8-32V 12V 24V to 9-46V 36V Voltage Regulator Booster Module Adjustable Voltage Step Up Power...
Who writes this atrocious copy?
 
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Thread Starter

Taymar

Joined Jan 13, 2017
31
Appreciate the help guys. This was really a proof of concept and I think the complexity and unknowns that the voltage booster introduced has made me go a different route.

Previously I'd found a piezo atomizer with a resonant frequency of 113khz, happily ran on low voltage but the output was weak. This 24v unit (2.7ghz res. freq.) had a much greater output, but the power requirements seem insurmountable for my application (even if the booster worked properly I think the current requirements would be difficult to guarantee).

Went back to the drawing board and think I've found the sweet spot. a 2.4ghz atomizer circuit that runs on 5v/1A. The output is somewhere between the other two, and is sufficient. Power reqs are much more inline with what the rest of the system can deliver without modification.

Thank you again for all the help and education.
 

Thread Starter

Taymar

Joined Jan 13, 2017
31
2.7ghz? 2.4ghz atomizer circuit?
Yes, sorry. That's not really relevant to the booster question - the device I was trying to power with the booster is a ceramic piezo disc driven by a circuit that delivers a 2.7Ghz signal. When this disc comes into contact with water, it turns it into very fine vapor, like a heavy fog or mist.

It seems that of the commercially available products, the larger (higher voltage) versions tend to use discs with a resonant frequency of 2.7Ghz and some of the smaller (lower voltage) desktop humidifier-grade options use a smaller disc at 113Khz resonant frequency. The quality and amount of fog is definitely better on the higher frequency units.

My application for this entire project is a fog generator that uses no chemicals or creates no residue, and I favored the water atomizer approach to avoid all the downsides associated with an oil burning heater element.
 

Thread Starter

Taymar

Joined Jan 13, 2017
31
Sure - the most common discs are I believe 16mm and 20mm. I don't have a data sheet I'm afraid - I purchased the whole thing ready made, but here's a link to some of the replacement discs (they are considered somewhat consumables), plus a couple of videos, one on modifying the larger power version into a more potent fog machine, and one on building the smaller lower power version from scratch. Only other thing I learned that could be relevant is from some of the DIY efforts I saw, people were struggling to generate a clean high frequency signal from the simpler circuits (555 timers etc.). Hope this helps!

https://www.amazon.com/s?k=humidifier+disc&ref=nb_sb_noss


 

Papabravo

Joined Feb 24, 2006
16,481
I think there might be a disconnect on the use of GHz, or gigahertz. That is 6 orders of magnitude larger than a kilohertz. There are NO mechanical devices I am aware of that vibrate at 2.4 GHz, or
\( 2.4 \times 10^9\;\text {Hz} \)
 

Papabravo

Joined Feb 24, 2006
16,481
Clean, high frequency signals are not really a problem if you can accurately specify what it is that you want. What I see is more akin to throwing spaghetti at a wall to see if it sticks.
 

Thread Starter

Taymar

Joined Jan 13, 2017
31
Thanks for this, will check it out!

---
Clean, high frequency signals are not really a problem if you can accurately specify what it is that you want. What I see is more akin to throwing spaghetti at a wall to see if it sticks.
And yes apologies if I'm technically inaccurate on any of this - frequencies or otherwise. I'm not and don't claim to be knowledgeable in this field at all. I simply know what I need (electronic mist generator with decent output at low voltage) and am trying to piece together readily available and relatively inexpensive pieces to get there. All I've got to go on is the various YouTube videos I've been able to find, and so that's the information I'm sharing. I should have been clearer on that as yeah, just because it's on the internet doesn't make it correct, point taken.

Thanks again for all the help.
 
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