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Supercapacitor Balancing Questions

e14 Contributor — Sun, 15 May 2016 18:57:48 GMT

Hello,

I have been doing some research for a couple months now on how to best balance supercapacitors in series. Now I'm just a hobbyist with only a college physics class and what I've read in my free time for an electronics background so I'm pretty limited. This in NOT a homework problem, Yay!

The attached circuit is what I came up with for balancing. It’s basically an active Zener shunt regulator across each bank of capacitors (all 2.5V 630F parallel and series for 5V 630F total). The hope is that if the capacitors reach 2.5V (or a little less just to be safe) the Zener diodes would start conducting, opening the NPN transistors, and shunt power to the capacitors with the lower voltage or stop charging them altogether. It will be powered via USB (5V, 2.1A) and will power USB up to 1A so I think the components will have to be pretty beefy.

[View:/resized-image/__size/944x852/__key/communityserver-discussions-components-files/70/contentimage_5F00_70255.png:944:852]

Ok for D1 I have a T6A100L 1kV 6A rectifier diode (probably overkill but it’s what I had) in series with a 18Ω, 5W resistor (R1) to limit current draw to the USB supply. For the bipolar NPN transistors Q1 and Q2, I’m thinking of using BUJ403A,127 transistors (550V, 6A, 100W) attached to heat sinks. Now for the problem(s). If I am to expect a 0.7V drop across the transistors, should I use Zener diodes with a Zener Voltage of 1.8V or 3.2V if I’m looking to limit the voltage to 2.5V. I’m also wondering if I need resistors at R2 and R3 to drop the voltage by 2.5V to make it safe for the capacitors in the other bank and pull current away from Zener diodes. If so, how would I go about determining the necessary values of R2 and R3? I included current limiting resistors R4 and R5 in series with each of the Zener diodes, but I don’t know if these are necessary or what value they should be to get the current to below 100mA. If resistors R4 and R5 are included would that change what Zener voltage I would need to use?

I also thought about putting all of the supercaps in parallel and using a buck converter to step the voltage from 5V to around 2.4V and ditch the balancing circuitry. The problem there is that the boosting the voltage back up to 5V. I’m using an Adafruit PowerBoost 1000 Basic to provide USB out but it only is operable down to 1.8V leaving me with only 3793J of useable energy instead of 6855J with the proposed setup. As this is meant for a mobile application that’s not a great option. I also looked at using the “ALD810024 Supercapacitor Auto Balancing (SAB) MOSFET” in a parallel configuration across the capacitors. However, this system is limited to around 80mA of current through it which seems insufficient to effectively drain these supercapacitors. Also it is in a surface mount SOIC-16 Package which even with a through hole adapter would stretch my soldering abilities. I currently have 20kΩ worth of resistors in parallel with the capacitor sets, however this doesn’t balance them very well and runs them down within a few days. I also looked at putting 3 rectifier diodes in series across the terminals of the capacitors; however, this is also limited in how much current can pass through it and I don’t know if it would be sufficient since I’m pushing 10.5W into these caps with the USB charger. Hopefully I covered everything. If you want to shoot some equations my way it would be much appreciated.

RE: Supercapacitor Balancing Questions

michaelkellett — Fri, 05 Jun 2026 14:34:02 GMT

Did you notice that the question is 10 years old and the last answer is seven.

I've been working on a super-capacitor buffered power supply with 10 x 400F caps in series. It has a micro to control balancing with up to about 3A current and measures the voltage across each cap.

Have you got a supercap project on the go ?

RE: Supercapacitor Balancing Questions

BillyVelasquez — Fri, 05 Jun 2026 14:09:22 GMT

This is an interesting discussion. One thing I learned when working with supercapacitors is that balancing becomes much more important than many people expect, especially when capacitors are connected in series. I like that you're considering several approaches instead of just relying on resistor balancing. The trade-off between efficiency, complexity, and long-term reliability is always the tricky part with these designs.

RE: Do I need to add more components to make this transformer safer?

geralds — Wed, 03 Jun 2026 10:46:28 GMT

..."Der Transformator-Spezifikation sagt 220 mA FLA. Ich weiß nicht, wie dein Leistungsbedarf für die Spieler ist, aber nur zum Spaß tu so, als wären die 25 VA Unity PF, also Watt. Der Transformator ist also vielleicht in Ordnung. Ich habe einen günstigen Blue-Ray-Player mit HDMI-Ausgang, der 10W und 12V bei 800 mA verbraucht."

Please don't merge two values: 10W / 12V/800mA DC is not the same as 115V/220mA AC.

Relatively, in his calculation with your player - in his player (i don't know??) is built-in a power supply, as well as a controller with buttons, a display, etc.. which need also a bit of "water".

Do I need to add more components to make this transformer safer?

HKPhysicist — Mon, 01 Jun 2026 16:14:36 GMT

Dear all Electrical and Electronic Engineers,

I own an audiophile grade Sony blue disc player. It accept 115V AC.

Then, I bought this transformer which transforms my wall outlet 230V AC to 115V AC, which is then connected to my Sony Disc Player.

https://hk.element14.com/triad-magnetics/vpt230-110/transformer-toroidal-2-x-115v/dp/1785731

Do you think whether I need to add additional components to make this transformer safer to work? I have already bought another beautiful aluminium enclosure to contain it. [emoticon:44a8a53ad3364ea78a16c5a3229f75bb]

The main point is - it is an audiophile grade system. Additional components may degrade the final sound quality.

So, there is a dilemma.

RE: Do I need to add more components to make this transformer safer?

geralds — Wed, 03 Jun 2026 07:16:40 GMT

ok! 👍

Your selection is ok. But i think it's a bit small.

Look for the next dimension, e.g. number of this transformer, https://at.farnell.com/triad-magnetics/vpt230-220/toroidal-power-transformer/dp/1785733

You can use it up to 440mA secondary if you connect the secondary parallel; 50VA. 50VA is enough for your application.

The primary must connect in serial.

http://www.farnell.com/datasheets/2279608.pdf?_gl=1*1ydhd2r*_gcl_au*Mjg3NDk2NzU0LjE3Nzg0MDY2MTg.

On the primary side you can mount a filter combined with a switch as well as fuses, https://at.farnell.com/xp-power/fgsma10bfr/iec-filter-medizin-200uh-10a-steck/dp/2992528

The housing must be a metal housing which is grounded to earth.

Be careful how you mount the transformer!

Or.... use this https://www.thomannmusic.com/tube_amp_doctor_transformer_230_115v_100va.htm

Best regards
Gerald

---

Bosch Plena LBB1935 schematic

jsmartins — Tue, 02 Jun 2026 23:11:46 GMT

Hello,

I have two Bosch Plena LBB1935 amplifiers that need repair. On the main bord there are some resistores with burn signs but i will nee the schematic to find the right values. Anyone have the circuit that can share a copy?

Thanks

José Martins

RE: Do I need to add more components to make this transformer safer?

colporteur — Tue, 02 Jun 2026 20:34:51 GMT

You are looking to purchase the unit? That is the need for the step-down transformer.

RE: Do I need to add more components to make this transformer safer?

HKPhysicist — Tue, 02 Jun 2026 20:18:21 GMT

It is a big sale from a USA dealer on ebay for US$100 a Sony audiophile grade blue disc player! What can be better?!? 😁

Then, I can watch 4k blue disc movie, high resolution CD, etc.

RE: Do I need to add more components to make this transformer safer?

geralds — Mon, 01 Jun 2026 21:42:39 GMT

Hi https://community.element14.com/members/hkphysicist ,

ähm? 🤔You have 230V AC and want to use a 115V disc player? Why not just get a 230V disc player?😎

Okay, okay… I don't know everything.

An analog solution might look good (“audiophile quality”), but your disc player is a digital device that converts digital signals into analog ones.

You can't hear that. A cheap power supply is therefore perfectly adequate for your needs.

What is the type of your Sony disc player? How is its power consumption?
May be this device has a built-in switch for selecting the main voltage.

RE: Do I need to add more components to make this transformer safer?

dang74 — Mon, 01 Jun 2026 21:31:07 GMT

I don't imagine the current draw on a disc player would be all that high, so on the surface 25VA doesn't seem that crazy to me... but I'd personally, I'd feel more comfortable knowing the player's current draw.

RE: Do I need to add more components to make this transformer safer?

robogary — Mon, 01 Jun 2026 20:52:18 GMT

No dilemma at all. IMHO, if you have an audiophile player, it has no audio power amplifier. As long as your power supply can supply the power peaks of the dynamic range, its OK.

That being said, 25 VA at 115 VAC is only about 210 mA.

Transformer spec says 220mA FLA. I dont know what your player power requirements are, but just for giggles pretend the 25 VA is unity PF, i.e. watts. So the transformer rated maybe ok. I have a cheapo blue ray player with HDMI output that uses 10W, 12V at 800 mA.

Anyway to get to the real point of your question, transformers, motors, etc are often fused unless they are impedance protected, i.e. their impedance is high enough that a short circuit doesnt overload the wiring.

This transformer has 12% voltage regulation from no load to full load, so without doing calcs, Id swagger short circuit current is enough that Id want to fuse the primary. 600mA to 1A slo blo would do the job.

RE: Do I need to add more components to make this transformer safer?

kmikemoo — Mon, 01 Jun 2026 17:14:51 GMT

If you're going with the toroidal transformer, be sure to use a bit of insulating mat under it. Typically, the ground plane is closest at that point and it stresses the insulation more than any other place in the insulating system. I agree with michaelkellett that 25VA is tiny for a power transformer.

RE: Do I need to add more components to make this transformer safer?

michaelkellett — Mon, 01 Jun 2026 17:03:02 GMT

The only way you will hear any difference is (perhaps) if you drop them both on the floor.

The transformer you have chosen should be fine if it's power rating is sufficient (25VA sounds very low for a high end player).

I would generally select a transformer with at least twice the VA rating of the load.

If the player has a mains earth connection make sure that you connect that as well.

RE: Do I need to add more components to make this transformer safer?

HKPhysicist — Mon, 01 Jun 2026 16:38:19 GMT

Yes, DIY only.

Because audiophiles like bigger power. Toroidal is also regarded as having less hysteresis. However, other persons prefer E type. They say E type sounds better. 😁

RE: Do I need to add more components to make this transformer safer?

colporteur — Mon, 01 Jun 2026 16:31:25 GMT

There are numerous step-down device for reducing AC for consumer electronics.

https://www.amazon.ca/Converter-Transformer-Switching-Household-Electronics/dp/B0FN6RL9LF/ref=asc_df_B0FN6RL9LF?mcid=e4879fff5de13fcea9fff60e8744ace0&tag=googleshopc0c-20&linkCode=df0&hvadid=766556333461&hvpos=&hvnetw=g&hvrand=1849706179935057473&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1002013&hvtargid=pla-2449076496662&hvocijid=1849706179935057473-B0FN6RL9LF-&hvexpln=0&gad_source=1&th=1

I grabbed the google link, please don't take this as an endorsement.

The AC input has the potential to impact audio if you have really dirty AC. I live in Canada where AC power is fair stable. Our Arctic regions where power is from diesel generators not so much.

Why the TOROIDAL choice for a solution? DIY project?

Clarification on AD7192 System Calibration Input Span vs Observed Full-Scale Behavior

Jay_Instrument — Sat, 30 May 2026 06:48:15 GMT

Hello,

We are currently evaluating the AD7192 ADC as a replacement for the obsolete CS5532 in our load cell application.

With the CS5532, after system calibration, we were able to achieve full-scale output at an input of 10 mV. While testing the AD7192, we are observing behavior that does not fully align with the system calibration input span specifications given in the datasheet.

Our configuration is as follows:

Reference voltage (Vref): 5 V
Gain: 128
Calculated full-scale input range (FS): 39 mV

As per the datasheet, the allowable input span for system calibration is:

Minimum input: 0.8 × FS ≈ 31 mV
Maximum input: 2.1 × FS ≈ 81 mV

However, our load cell has a maximum output of 10 mV, which is significantly below the specified minimum calibration span.

Observed behavior:

We tested inputs at 10 mV, 15 mV, and 30 mV.
We begin to observe full-scale counts starting at approximately 15 mV.
This is notably lower than the expected ~31 mV minimum based on the datasheet.

Questions:

What could explain achieving full-scale counts at ~15 mV, which is below the specified minimum system calibration span?
Is this behavior valid and reliable for production use, or could it lead to accuracy or stability issues?
Given our load cell output (max 10 mV), would you recommend proceeding with AD7192, or should we consider alternative configurations or devices?

Additionally, could you please connect us with an Analog Devices application engineer to further investigate and discuss this issue in detail?

We would appreciate your guidance in understanding whether this observed behavior is within acceptable operation limits and suitable for long-term use.

RE: Clarification on AD7192 System Calibration Input Span vs Observed Full-Scale Behavior

michaelkellett — Sat, 30 May 2026 08:32:17 GMT

You need to describe your set up in more detail.

Check out the Data Output Coding on page 32 of the data sheet. Are you working in uni-polar or bipolar mode.

Another possibility is that you are nor reading the device output correctly but are shifting the data by 1 bit at some point.

You should be aware that E14 is a forum with a wide range of members and while you may get direct support from Avnet/Farnell/Newark you may not.

If you want support from AD you should contact them directly.

I don't work for any of the above and my suggestions are based on general experience of load cells and ADCs and looking at the device data sheet.

ERSA soldering iron tip suddenly un-tinnable

davebullockmbe — Sun, 17 May 2026 09:53:03 GMT

Hi I have an ERSA I-CON PICO solder station that has served me really well for several years when suddenly the 'pencil' tip has become un-tinnable.
It is the :-

://uk.farnell.com/ersa/0102pdlf04-sb/tip-soldering-iron-pencil-0-4mm/dp/1203967

A 0.4mm pencil tip which is great for getting into solder the tiny legs of SMD IC's.
I had used ERSA Digital 2000A's for years and years and then bought two of the I-Con Pico's (one for me and one for my son) a few years ago as we are both into SMD development and assembly.
I have never had a problem with the tip of the iron until recently when I just couldn't get the very tip of the bit to accept solder.
The solder station is not used on a daily basis (hobby use only) and is only switched on when required, I always use the supplied brass (Brillo pad) tip cleaner and this has kept the tip clean and operational until now.
Inspecting the tip I can see that it is still sharp with no visible pitting or corrosion, however it has a grey appearance instead of a 'silver' tinned area right at the tip.
I imagine that these tips have a special coating and shouldn't have anything abrasive applied (sandpaper/file etc) so I am wondering if the tip can be easily restored, or has it reached the end of it's life??
Any suggestions would be gratefully received, as both solder stations are suffering the same problem.

Thanks ...Dave

RE: ERSA soldering iron tip suddenly un-tinnable

Jan Cumps — Thu, 21 May 2026 09:26:45 GMT

I have used these products to revive tip wetting issues:

They aren't general maintenance solutions. Intended to recover what otherwise would be a throwaway.

Would someone be interested to create Ben Bulsink's NFC Game Board?

Luka851 — Mon, 18 May 2026 13:10:51 GMT

Hello everyone,

I wanted to make a custom smart chess board and I came across to Ben Bulsink's open source technology on nfcgameboard.com. Following is a demo video of his creation: https://www.youtube.com/watch?v=4qKndjF60Js&t=12s.

I wrote to him, and together we decided to upgrade the device and use the newer PN5180 IC instead of the CLRC632 IC that he used in the prototype. We used Playfultechnology library for PN5180 and encountered issues, such as the library wasn't detecting multiple tags. We have solved and improved that library, and that challenge now is solved, however we now encountered next issue which is connecting the IC to the external antenna. When we cut the PCB antenna traces on the module the IC stops to respond correctly, such as returning EEPROM and seems to get stuck in the loop even before it reaches communicating with the antenna. We don't know what may be causing this. Does anyone has any idea on it and how to fix this?

My next question is will there be anyone who would be curious enough to also try to recreate the improved board? We want to create an open source technology - hardware as a sandbox, so anyone can make the board, and then write their own code to create any kind of the game on top on it, whatever they want, perhaps share their game on the common platform with other players to download and play their games. We are communicating through email and having more brains working on it will make things easier, faster, and thought maybe ask if anyone was interested to join, will be here to help and explain, what I know.

https://nfcgameboard.com/schematics/ - gives the idea, schematics, pcb, and similar, but for CLRC632. in short, we will make 15x15 grid board, using multiplex antennas - each antenna being 15x30mm, we will have then 30 antennas (15 rows, and 15 columns), instead of 225 small antennas, a matching circuit and one PN5180 IC.

RE: Would someone be interested to create Ben Bulsink's NFC Game Board?

jc2048 — Thu, 21 May 2026 09:17:59 GMT

"Does anyone has any idea on it and how to fix this?"

Maybe it's trying to protect itself from your coil. I've never worked with NFC, but it seems obvious that there would need to be a way for the chip to protect itself from any items placed into the volume of the operating magnetic field that would, in effect, 'short' the field. A technology used extensively, like this is, needs to be pretty robust and difficult to kill. Imagine the economic mayhem if you could put a card reader out of action with a simple shorted turn. With a low frequency transformer, you'd rely on a fuse to get you out of trouble with a shorted secondary, but here it would either be indirect with a temperature monitor or directly by looking at the current supplied to the TX drive. It's possibly a bit complicated because of the need to power 16 tags simultaneously over a short period with the ISO scheme to enumerate them, so maybe it can't simply be a sensible limit easily within the dissipation limit of the chip - there possibly needs to be a time element to it as well.

If the resonance of your makeshift coil with the parallel capacitance on the board is a long way from the operating frequency, it will look like a heavy load to the chip.

Just a theory.

If you know the parallel capacitance on the board, perhaps you could try the same capacitance alone with the coil, find the resonance, and then adjust the coil so the resonance moves back to 13.56MHz. Then your coil's inductance will match that of the one on the board. Use a good quality SMD cap, similar to the ones on the board (if you use an old leaded part, you'd just be measuring the self resonance of the cap). You could probably get it close enough to function, even if it's not spot on. After all, it can't be too hard a resonance because the signalling sidebands are so far away from the centre (800kHz is it?) and they'll want a reasonable signal level for the RX detection.

The grid of coils is an interesting idea, but what would you use to do the multiplexing? Lots of RF relays?

RE: Help identify replacement for burnt out component

stanto — Wed, 20 May 2026 22:08:07 GMT

Unfortunately I was not in a position to replace those parts within the time and resources available, surprisingly getting hold of parts like this in Norway is not trivial.

Help identify replacement for burnt out component

stanto — Sat, 16 May 2026 15:55:41 GMT

I have been asked to repair the charger for a family member's E.C. Cutter Electric Scissors Kit. The charger for it is supposed to output 7.5v at 1.2a and it outputs 11v and buzzes. It's completely sealed, so it's going to be replaced.

However it took the charger with it, upon opening it should a replaceable component, but I'm having trouble knowing what to look up.

Here's photos of its insides:

I'm presently in Norway, so finding parts here may be tricky and I'll have to bring it back to England to pick something up!

I'm expecting some of the diodes to have failed after checking them in diode mode on a multimeter, and the burnt out component may be a radial inductor?

Has anyone worked on Integrating with openplotter for AIS ADSB marine Ham band monitoring?

KariR — Wed, 20 May 2026 12:33:57 GMT

I'm interested in replacing my sdr dongles with this kit to integrate AIS ADSB Marine and Ham band monitoring. The capabilities of the kit fit nicely and will allow for simultaneous wideband monitoring over a very wide spectrum