Power filter/capacitor board for custom build pinball machine - Page 1
Forum section: electronics / beginners

author: Raymond175
author_rank: Newbie
timestamp: May 28, 2019, 07:34:52 pm
content: Hi all, I'm Raymond and I just joined this forum!I'm in a very long running project (several years) to build a custom pinball machine from the ground up, which includes woodworking, photoshopping, software development, electronics, etc. I'm a software developer and I'm very eager to learn everything that is needed to complete my project.Currently I'm facing a power issue in my flipper circuit. As soon as one of my flipper fires, my power supply will "shut down" because of the short circuit protection due to the sudden draw. Therefore I need add a power filter board or capacitor board to "buffer" and offload the power supply. I can buy ready-to-use boards for pinball machines online, but I want to build/design it custom and add more functionalities later, like a coin door interface (which cuts high voltage when the coin door is open) and a 48V to 5V step down convertor (to power my Arduinos via the same power supply).Now I have very basic knowledge of electronic engineering and basic knowledge of components. And with some logical reasoning I can come quite far with designing my own circuit boards, but my main problem is that I have no clue on figuring out which brand or model of certain electronic components to use and why...What components I think I'll need to create such a board:Connector pins (and cable connectors) for 48V 6.7A power supplyCapacitorsThermistor (to prevent the capacitors from triggering the short circuit protection)Multiple power railsHigh voltage LED(s) (for visually indicating that the capacitors are charged as well as draining them)Connector pins (and cable connectors) for supplying other components (like the flippers) of power and ground via one of the power railsFuse holders and fuses for protecting the power supply (if needed?)My questions:Do I need any more components?How to decide which connector pins to use for 48V 6.7A? Which can also be easily (dis)connected but will stay connected when in useHow to decide which and how much capacitors to use? A board I saw online had three 8200uF 63V 85C capacitorsHow to decide which thermistor to use?How to decide which LEDs to use?How to decide which type of fuse holders and which type of fuses to use?Components:Power supply: Mean Well, SP-320-48Capacitor: Cornell Dubilier, SLPX822M063H5P3 (?)Thanks in advance for any reply!RaymondPS1: The power filter board that I used for inspiration can be found here:http://docs.missionpinball.org/en/dev/hardware/fast/power_filter.htmlPS2: The pinball machine I'm trying to build is a copy of the Tales Of The Arabian Nights (TOTAN) of Williams:

author: Kjelt
author_rank: Super Contributor
timestamp: May 28, 2019, 08:01:31 pm
content: Just my two centsFor the relais and coils you actually don't want a switch mode power supply with overvoltage and overcurrent protection.Just use what the 50s to 90s pinnballs used, a beefy transformer with beefy rectifier and fat electrolytic capacitors. The coils don't care if the unloaded voltage is a couple of volts to high as long as it can quickly draw current and won't choke on the reverse emf voltage.That is what probably is happening. If you release the voltage to a powerfull coil it will try to keep that current going and it will raise the voltage. To protect you have a diode across the coil. You do have the diode across the coil close to the coil do you?When a modern smps detects that overvoltage it can shut down. Even when it happens too often it can damage the smps.The good news powerfull transformers are not that wanted anymore so you can buy them for the copper price. Only the electrolytics might be expensive so try to find good 2nd hand A brands.

author: floobydust
author_rank: Super Contributor
timestamp: May 28, 2019, 08:11:11 pm
content: Sometimes you keep a flipper up, to catch a ball or poke it.Pinball machines had a set of contacts on the flipper, so full voltage to get it moving fast and then when the flipper is almost up, switches to a lower holding voltage so the coil does not burn up.

author: Raymond175
author_rank: Newbie
timestamp: May 28, 2019, 08:23:47 pm
content: Quote from: floobydust on May 28, 2019, 08:11:11 pmThe problem is not in the flipper circuit (or coils), but in the sudden draw of power/current by the flipper circuit when they get activated. The coils indeed have 2 separate windings, one large for the powerfull kick an one small for holding the flipper up. This all works fine and are actual original new flipper components. My problem is the sudden draw, which can be from one, two (e.g. flippers) or even six (flippers, kickers, magnets, multiball, etc.) high voltage coils at a time.

author: Raymond175
author_rank: Newbie
timestamp: May 28, 2019, 08:30:50 pm
content: Quote from: Kjelt on May 28, 2019, 08:01:31 pmThe whole flipper circuit are original new flipper mechanics, which indeed do have the flyback-diodes between the high and low windings of the coils. But this all works fine, my problem is really the sudden draw, which can be from one, two (e.g. flippers) or even six (flippers, kickers, magnets, multiball, etc.) high voltage coils at a time.This actual power supply that I'm using was recommended by the pinball community. I'm aware of the old power supplies used in the original pinball machines, but these are actually very hard to get, as they seem to not being manufactured anymore.But since I'm also going to power so much more than only coils, think of the microcontrollers (Arduinos), lighting, backsplash, display, etc. having this type of power supply with actual protection seems logical to me.

author: ogden
author_rank: Super Contributor
timestamp: May 28, 2019, 08:36:50 pm
content: Quote from: Raymond175 on May 28, 2019, 08:23:47 pmThen conclusion is simple one: your power supply is not powerful enough.

author: Raymond175
author_rank: Newbie
timestamp: May 28, 2019, 08:45:17 pm
content: Quote from: ogden on May 28, 2019, 08:36:50 pmI appreciate your reply, but there is nothing wrong with this power supply in this setup. A pinball machine uses about 1 - 2 amps with some spikes to 4 amps, so 6.7A is powerful enough. Also every pinball machine has a power filter/capacitor board to "buffer" the power/current to prevent drops when coils get activated. And this exact power supply has been used in tons of home build pinball machines by the FAST Pinball Project.You are all focusing on my power supply and actually ignoring my actual question about how to figure out which brand/model of components to use to build such a power filter/capacitor board.So again, here is the power supply recommended:http://fastpinball.com/platform/hardware/fast-power/power-supplies/And here is the power filter/capacitor board recommened:http://fastpinball.com/platform/hardware/fast-power/fast-power-filter-board

author: ogden
author_rank: Super Contributor
timestamp: May 28, 2019, 09:01:51 pm
content: Quote from: Raymond175 on May 28, 2019, 08:45:17 pmYour chances that some1 here in this forum built pinball machine, used same supply, experienced same problems and solved them are... slim. So, please do not become agitated when we are suggesting either obvious or just random solutions. What kind of power filter/capacitor board you are using? You can provide voltage/current waveforms and we could possibly solve your problem using "common sense engineering approach" or we are just chatting and suggesting what comes into mind

author: Raymond175
author_rank: Newbie
timestamp: May 28, 2019, 09:06:02 pm
content: Quote from: ogden on May 28, 2019, 09:01:51 pmThe problem is that for now nobody actually replied to my question but replied to parts of my post containing information about the current situation.Like I said in my post, I don'thavea power filter board, I want tobuildone and therefore I need some advice on components.

author: ogden
author_rank: Super Contributor
timestamp: May 28, 2019, 09:15:05 pm
content: Quote from: Raymond175 on May 28, 2019, 09:06:02 pmYou need some resistors and capacitors You can get quality answer when you provide quality data. W/o current & voltage waveforms nobody can tell you anything about components you have to use in capacitor bank. In your place I would just "reverse engineer" existing capacitor bank, maybe consult some "DIY pinball" forum (or individual) about components used in such.QuoteThis is public forum. Nobody is obligated to reply anything

author: Brumby
author_rank: Unknown
timestamp: May 29, 2019, 01:26:09 am
content: I've had a look at the board you linked to - and the only functional part of that which relates to your issue is the 3 big capacitors....If it were me, I'd be looking at something like 2000uF or more for each capacitor with at least 60V working voltage (based on the 48V power supply). (Would be good to see what value are actually used.) I'd also be looking for a low ESR to allow big current surges to pass.The caution here is to not have too great a capacitance and too low an ESR that the power supply will object to charging them up when the machine is turned on.

author: Brumby
author_rank: Unknown
timestamp: May 29, 2019, 01:53:23 am
content: Quote from: Brumby on May 29, 2019, 01:26:09 amHad a look at the Open Pinball Project and for their power filter board they have specified 8.2mF - which is 8,200uF - at 63V for each of these 3 capacitors. They also give a Mouser part number: 598-SLPX822M063H5P3. This capacitor has an ESR around 0.05 ohms, which seems appropriate to me.

author: Raymond175
author_rank: Newbie
timestamp: May 29, 2019, 04:38:14 am
content: Quote from: Brumby on May 29, 2019, 01:53:23 amI had to search quite a lot for the information you mentioned, but I have found the page with Mouser part numbers! That is a great help for me at this stage.Although the Open Pinball Project doesn't use fuses, and I don't know if I even need them... what do you think?

author: Brumby
author_rank: Unknown
timestamp: May 29, 2019, 05:31:21 am
content: Fuses are cheap and easily replaceable. If they blow, it will be for a reason and will usually save you from a more expensive failure.

author: Kjelt
author_rank: Super Contributor
timestamp: May 29, 2019, 09:21:27 am
content: Quote from: Raymond175 on May 28, 2019, 08:30:50 pmThat problem is only for the HV supply since that powers the coils and relais.Yes you can use the proposed switch mode power supply (smps) BUT then you need a capacitor bank to buffer the peaks, that is what you are now doing.A possible issue with this solution can be that the smps will oscillate.Normally a switch mode power supply (smps) does not like to have huge capacitance on its output since it disturbs the control loop.This can often be found in the datasheet , but I can not find it in the Meanwell datasheet so it is going to be a trial and error.My suggestion was to build a normal standard powersupply from available components, not to buy a pinball power supply, just build your own.The transformers can be get really cheap 2nd hand and the rectifier are also not the costs. The capacitors are expensive but you were going to buy them for your buffer anyway.

author: mvs
author_rank: Frequent Contributor
timestamp: May 29, 2019, 10:42:13 am
content: Quote from: Kjelt on May 29, 2019, 09:21:27 amNTC thermistor, fuse and wires will introduce some parasitic resistance and inductance to the circuit. It may be sufficient to isolate supply from caps.

author: ogden
author_rank: Super Contributor
timestamp: May 29, 2019, 10:52:59 am
content: Quote from: mvs on May 29, 2019, 10:42:13 amEven better solution is P-channel MOSFET in-rush current limiter.Circuit fromhttps://www.onsemi.com/pub/Collateral/AND9093-D.PDF

author: mvs
author_rank: Frequent Contributor
timestamp: May 29, 2019, 11:28:57 am
content: Quote from: Raymond175 on May 28, 2019, 07:34:52 pmEither you have a preferred connector type (like molex mini-fit, KK396, KK508 ...) or you can use parametric search (digikey.com, mouser.com ...).QuoteYou will need a NTC thermistor for inrush current limiting. I would start with around 5 Ohms and 10A rated (~ 25-30mm diameter) NTC.QuoteI would go for some basic 5mm diffused LED and 2mA current drive. Current limiting resistor is then 22KOhm ( (48-3)/0.002=22K ), 0.25W ( (48-3)*0.002=0.09W + some safety margin).

author: Raymond175
author_rank: Newbie
timestamp: May 30, 2019, 08:16:03 am
content: Ok, thanks I've got some great replies now!I've drawn a diagram (and I'm new to this, so bear with me) with the following features (or at least what I intended):* Indicator LED on circuit (capacitor decharger)* Multiple power rails (for flippers, for slingshots, etc.)* Fuses on all power rails* Indicator LED on all power railsIs my diagram and idea correct?Thanks,Raymond