MiSTer FPGA Forum

Hi guys. Can anyone recommend a good, preferably US-based seller for an in-line power switch for MiSTer? I had read about voltage drop issues with some units in the past, and I'd like to make sure that I'm purchasing one that isn't going to give me any trouble. Thanks

The ones I got look the same as these: https://www.amazon.com/PLUSPOE-Extensio ... B07PDZKLF7 I took voltage measurements with a multimeter and mine do not change the voltage at all.

Just try them and if you have a multimeter, test them.

Took one for the team and ordered the one Threepwood linked to. I can confirm that there's no issues with these. I tested it with my multimeter and there's no voltage drop or any other oddities. I don't like throwing good money after bad, even if it is just a couple of bucks, so for other people like me looking this up in the future, go with these, especially if you need a 2 pack like I did. They're cheap and they work fine

Can someone give an explanation of how to test for the voltage drop with a multimeter? I'm not sure where to put the leads.

justaguy wrote: ↑Thu Jun 18, 2020 5:43 pm Can someone give an explanation of how to test for the voltage drop with a multimeter? I'm not sure where to put the leads.

What I did was plug in just the power brick without the switch attached, then set my multimeter to read DC voltage in the 20v range (yours might be slightly different). Then, since the plug is center positive, i touched the black probe to the outside of the plug barrel and put the red probe inside the barrel. I got a reading of about 5.2v, which is normal since there's nothing drawing power from it at the moment. Next I attached the switch, and set up my probes the same way at the output. When the switch was on, I got the same reading of about 5.2v, when it was off I got 0.0v. Since everything matched up when it was on, and there was no voltage leaking when it was off, I was good to go.

colonel panic wrote: ↑Thu Jun 18, 2020 7:13 pm What I did was plug in just the power brick without the switch attached, then set my multimeter to read DC voltage in the 20v range (yours might be slightly different). Then, since the plug is center positive, i touched the black probe to the outside of the plug barrel and put the red probe inside the barrel. I got a reading of about 5.2v, which is normal since there's nothing drawing power from it at the moment. Next I attached the switch, and set up my probes the same way at the output. When the switch was on, I got the same reading of about 5.2v, when it was off I got 0.0v. Since everything matched up when it was on, and there was no voltage leaking when it was off, I was good to go.

Thanks for the noob-friendly explanation! It seems totally obvious in hindsight...

Anyway, I just checked the switch I've been using and got the same results as you did, so that's a relief. Purchased from this Amazon listing for what it's worth.

You really should check them under load. Hook everything up, power up, and measure voltage at the de-10 barrel jack.
I've only ever come across one decent batch of these switches, haven't been able to get more 'good' ones.

legacypixels wrote: ↑Fri Jun 19, 2020 2:12 pm You really should check them under load. Hook everything up, power up, and measure voltage at the de-10 barrel jack.
I've only ever come across one decent batch of these switches, haven't been able to get more 'good' ones.

OK, I tried this and did see a drop from about 5.15V without the switch to almost exactly 5V with, but I should be OK since the DE-10 nano is expecting 5V anyway, right? This was with the Genesis core running Sonic 1, is there a heavier load I should try to be sure?

That looks good

I know this is an old topic but can someone confirm what Mister power switches are safe to use (I mean no voltage drop)? Is this one behind the link high quality? It says that "Minimal Voltage Drop" but has someone really measured it? At least the seller should be reliable, I think.

https://misterfpga.co.uk/product/mister ... er-switch/

Pretty sure i did see that someone measured misterfpga´s switch sometime (could have been a long time before!) before i bought my de-10 in july last year.
i have used it in my setup with de-10/digital io board/blisster since and have worked fine (which off course is NOT certain that all switches will).

But to be really sure you should probably measure any and all switches BEFORE using any of them.
Since everything that is made will have a certain failure rate even from the worlds best/leading maker of that thing (except the MiSTer Project and sorgelig off course ).
See/google bell curve and or normal distribution for more info on that.

Yes, this a is good way to go, but unfortunately I don't have multimeter. Maybe Nat, who runs the mister.fpga.co.uk store, can say something about this.

I bought one from mister.fpga.co.uk and have had no problems.

I bought this (I'm in UK) and it works great https://www.amazon.co.uk/gp/product/6041053481/

I don't know what to believe because some people say that the system may still work even under-voltaged but it can be dangerous.

I'd like to know what exactly a switch with a little voltage drop is going to do to the system? I'm struggling to see how damage could be done by not having a high enough voltage. Instability in the cores / output, sure but damage? Someone please explain so that I know. Ta.

Anyone interested in some cool looking old knife switches?
https://www.ebay.ca/sch/i.html?_from=R4 ... +&_sacat=0
Would be kinda cool to have for the mister.

guddler wrote: ↑Mon Mar 08, 2021 11:42 am I'd like to know what exactly a switch with a little voltage drop is going to do to the system? I'm struggling to see how damage could be done by not having a high enough voltage. Instability in the cores / output, sure but damage? Someone please explain so that I know. Ta.

To be honest, I don't know if it really is dangerous. This text is taken from Retro RGB:

Several users have reported voltage drops when using 5.5mm barrel plug power switches with the MiSTer. Three people have now tested them on a multi-meter and the results are shocking “5.1v normally, 4.2v w/switch” –Lo-Fi

Although the switches may “work”, they are dropping the voltage to dangerous levels. Symptoms include boot failures and the fan running slowly or not spinning up at all. I strongly advise against them, even if they “work”. Under-volting electronics is bad, mmkay…

https://www.retrorgb.com/mister-power-s ... rning.html

The issue is that the China-supplied switch/splitter unit has been shown (in the past - on the previous forums) as having measurable resistance, which causes a voltage drop. Which does not mean to say that a switch cable is inherently a bad thing. Only that those cables were bad.

Since that time, other suppliers with similar-looking switch assemblies have demonstrated better characteristics, so some sellers like misteraddons are including those from suppliers they have found to meet requirements.

However, the original bad suppliers are - as far as I can tell - still selling the problematic switches. And the average consumer may not be able to tell the difference as they look the same, until the resistance is measured.

So then I assume it is safe to use switches, for example, sold by misterfpga.co.uk.

venalaine wrote: ↑Mon Mar 08, 2021 7:59 pm

guddler wrote: ↑Mon Mar 08, 2021 11:42 am I'd like to know what exactly a switch with a little voltage drop is going to do to the system? I'm struggling to see how damage could be done by not having a high enough voltage. Instability in the cores / output, sure but damage? Someone please explain so that I know. Ta.

To be honest, I don't know if it really is dangerous. This text is taken from Retro RGB:

Several users have reported voltage drops when using 5.5mm barrel plug power switches with the MiSTer. Three people have now tested them on a multi-meter and the results are shocking “5.1v normally, 4.2v w/switch” –Lo-Fi

Although the switches may “work”, they are dropping the voltage to dangerous levels. Symptoms include boot failures and the fan running slowly or not spinning up at all. I strongly advise against them, even if they “work”. Under-volting electronics is bad, mmkay…

https://www.retrorgb.com/mister-power-s ... rning.html

Undervolting electronics is typically bad for them though, so it is dangerous, if you consider things that damage your electronics to be a danger.

venalaine wrote: ↑Tue Mar 09, 2021 6:58 am So then I assume it is safe to use switches, for example, sold by misterfpga.co.uk.

I would assume that they've done their homework so that you don't have to... but I haven't specifically used their products.

aberu wrote: ↑Tue Mar 09, 2021 3:13 pm Undervolting electronics is typically bad for them though, so it is dangerous, if you consider things that damage your electronics to be a danger.

Saying that it's "typically bad for them" doesn't really explain much though. I mean, I'm not trying to be awkward here, I'm just trying to get to the bottom of it. If there's an actual known issue, then fair enough, I'll go and measure voltage drop across my switch (on the board, under load), but does anyone know what it actually is? Or is this just internet whispers?

For example, there's a bank of RAM on one of the boards in a Sega G80 cage where the chips need -12v and will physically die, pretty quickly, if you instead supply them with -5v which a lot of people do because Jamma standard supplies -5v. So that's a good example where PCBs will quite literally be killed by undervolting the -12v line to around -5v. I forget the RAM chip but I have a feeling it's 4027?

Are we talking something like that? If so, what?

Searching "brownout electronics damage" might provide some more info on undervoltage conditions. For example, I found this regarding PSUs:

"In a brownout, power supplies need to draw more current to compensate for the lower supply voltage, which is very stressful for transistors, wires, diodes, etc. They also become less efficient, which makes them draw even more current, aggravating the problem."

In other words, if there is prominent voltage drop it's possible that de10-nano might die sooner than without using the In-line power switch.

guddler wrote: ↑Wed Mar 10, 2021 12:38 am

aberu wrote: ↑Tue Mar 09, 2021 3:13 pm Undervolting electronics is typically bad for them though, so it is dangerous, if you consider things that damage your electronics to be a danger.

Saying that it's "typically bad for them" doesn't really explain much though. I mean, I'm not trying to be awkward here, I'm just trying to get to the bottom of it. If there's an actual known issue, then fair enough, I'll go and measure voltage drop across my switch (on the board, under load), but does anyone know what it actually is? Or is this just internet whispers?

For example, there's a bank of RAM on one of the boards in a Sega G80 cage where the chips need -12v and will physically die, pretty quickly, if you instead supply them with -5v which a lot of people do because Jamma standard supplies -5v. So that's a good example where PCBs will quite literally be killed by undervolting the -12v line to around -5v. I forget the RAM chip but I have a feeling it's 4027?

Are we talking something like that? If so, what?

https://electronics.stackexchange.com/q ... volting-it <-- It depends.

There's all kinds of information here.

Disclaimer: Not an electrical engineer, just someone who reads up on a wide variety of topics as a hobby.

FPGA's are sensitive electronics. The Cyclone V is a CPLD (it has an ARM processor embedded in addition to the FPGA and few other pieces), the ARM processor should try and mitigate the damage of a brownout or undervoltage scenario (and overvolt) similar to how your personal computer's processor. However, that doesn't mean it is inoculated against the kinds of damage indicated in this thread.

An FPGA is basically a series of logic gates and RAM blocks (and other things like xtal, etc... most of the time) that can be "wired" together in a way that is similar to you writing data to RAM (please no FPGA snobs jump down my throat, it's an approximation of what's happening, and they are indeed described this way - https://www.electronicdesign.com/techno ... s-of-fpgas <-- read the static ram section if you disagree). The Cyclone V doesn't hold onto it's program after the power is shut off, therefore it is a "SRAM-based FPGA" type. Basically when power is provided to it and the FPGA is programmed from some memory source (in our case the MicroSD which contains the programs and operating system that the ARM side uses, and the rbf files which are your FPGA designs) it does stuff, and when you pull the plug, it gets wiped clean again, just like RAM.

What happens when you undervolt SRAM? It's going to fail a lot sooner than it would if it were ran at the spec. Obviously the Cyclone V has the ARM processor's capabilities to prevent any prolonged undervolting, so it may do something like shut off the system if it doesn't meet the threshold for voltage that the engineers at Altera/Intel have decided is an appropriate minimum. I don't know for sure, but that's typically one of the main advantages of a CPLD (that has an FPGA) over "just" an FPGA is.

I'm not an electrical engineer so my knowledge won't stretch into the explanation in terms of physics or anything like that.

It would be nice to hear what some hardware oriented developers in Mister community think about the subject. And of course there are some other FPGA guys (Krikzz & Kevtris etc...) who surely know how this goes but maybe they don't want to say anything related to Mister.

It would also be useful if the DE-10 Nano user manual actually had anything at all on the topic of power. But then I guess they are going to just assume you're using the power supply that it came with and no inline switch. Which I'm not because it was an EU power supply and while I could have used an adapter, that's clunky and I had a UK one suitable for the job

I'm using a 5A power supply, which is probably overkill. I literally had to step on the plug of my switch, to squash it a bit, to make the contact work.

guddler wrote: ↑Wed Mar 10, 2021 1:50 pm It would also be useful if the DE-10 Nano user manual actually had anything at all on the topic of power. But then I guess they are going to just assume you're using the power supply that it came with and no inline switch. Which I'm not because it was an EU power supply and while I could have used an adapter, that's clunky and I had a UK one suitable for the job

Not the de10, but the Cyclone V datasheet has power specs: https://www.intel.com/content/dam/www/p ... _51002.pdf