PSU puts out 23.8v  

  RSS
farina
(@farina)
Eminent Member

My MMU2S keeps crashing. I’ve read and watched Prussia videos about all LEDs flashing indicating low power. I never really thought I had a problem until today. Again I am back to crashing and so I grabbed the multimeter and realized I am at 23.8v right at the lugs on the PSU. I can measure this all the way to the MMU2S and I get the same result. 

Is this abnormal or within tolerance?

Best Answer by morphias:

Posted by: @tim-m30

With what meter? True RMS reading, avg rms reading, etc.  23.8 is probably reasonable for a typical chinese 24v supply. 99.2% of the desired value. And considering the last calibration date of your meter (or if an inexpensive meter - no calibration) ... 

I'd say not to worry about it.

 

As a qualified electrician,  I agree.

 

23.8V is about what you would expect to see.

 

 In fact, I've just pulled out my Fluke multimeter (which is in date) and checked my MK3S. I see 23.87-23.88V at idle and at full load with a bed and nozzle preheat running, both fans at 100% whilst doing an auto home.

 

I dont think voltage is your issue.

 

Ben.

Posted : 19/10/2020 6:15 am
--
 -2
(@-2)
Illustrious Member

With what meter? True RMS reading, avg rms reading, etc.  23.8 is probably reasonable for a typical chinese 24v supply. 99.2% of the desired value. And considering the last calibration date of your meter (or if an inexpensive meter - no calibration) ... 

I'd say not to worry about it.

 

It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 19/10/2020 7:32 am
morphias liked
morphias
(@morphias)
Eminent Member
Posted by: @tim-m30

With what meter? True RMS reading, avg rms reading, etc.  23.8 is probably reasonable for a typical chinese 24v supply. 99.2% of the desired value. And considering the last calibration date of your meter (or if an inexpensive meter - no calibration) ... 

I'd say not to worry about it.

 

As a qualified electrician,  I agree.

 

23.8V is about what you would expect to see.

 

 In fact, I've just pulled out my Fluke multimeter (which is in date) and checked my MK3S. I see 23.87-23.88V at idle and at full load with a bed and nozzle preheat running, both fans at 100% whilst doing an auto home.

 

I dont think voltage is your issue.

 

Ben.

This post was modified 1 month ago by morphias
Posted : 19/10/2020 12:54 pm
farina
(@farina)
Eminent Member

@tim-m30

I'm using a Fluke 117 True RMS. @morphias that answers my question for sure. I wonder why this damn MMU2S keeps giving me the 10 LED salute?

Thanks!

Posted : 19/10/2020 4:27 pm
jsw
 jsw
(@jsw)
Noble Member
Posted by: @farina

My MMU2S keeps crashing. I’ve read and watched Prussia videos about all LEDs flashing indicating low power. I never really thought I had a problem until today. Again I am back to crashing and so I grabbed the multimeter and realized I am at 23.8v right at the lugs on the PSU. I can measure this all the way to the MMU2S and I get the same result. 

Is this abnormal or within tolerance?

I measured my PS when I made some recent mods, and IIRC it was 23.9.  If you are 23.8, you are within 1% and if you have issues it's probably something other than low voltage per se.  If it's DC, 'true RMS' or whatever should not make any difference.  One thing you might do if you have a 'scope is to check for ripple and noise in the power supply.  My guess is that if you indeed have severe ripple, you would have other issues as well.  However, my guess is that things like loose/dirty connections or lead resistance may be more relevant here if the MMU does not behave properly.

 

Posted : 19/10/2020 4:36 pm
--
 -2
(@-2)
Illustrious Member

Actually @jsw, a good meter that measures DC also includes any noise on the bus, and a having true RMS measures that noise more accurately than other meters.  Usually having a bandwidth spec included. Since most of the supplies used in printers are LED power supplies - known for high noise - it makes a difference. I've more or less given up on normal terminology in this forum, noise vs ripple & noise, but measurement is what I did for years before retirement. Even building tools to measure the pressure in those ion diffusion pump systems you worked with.

It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 19/10/2020 5:34 pm
jsw
 jsw
(@jsw)
Noble Member

Well, I guess I must not be experienced with 'good' test equipment then!

Posted : 19/10/2020 5:43 pm
--
 -2
(@-2)
Illustrious Member

Well - that isn't what I was saying, but, okay. Meters, whether good or bad, and unless great pains are taken to somehow remove the AC component from the A-D digitization process, will include AC in the DC measurement. Some better meters will call it DC+AC ... and some meters will include DC when measuring RMS, other filter out DC for RMS measurements (in a sense, AC coupling). So yes, the meter you are using matters.

It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 19/10/2020 5:59 pm
--
 -2
(@-2)
Illustrious Member

ps: the major difference when a meter measures AC on top a DC signal is how that energy is converted during the A-D process. True RMS meters will calculate area under the curve, less expensive meters assume a sinewave (peak * .707 - or worse, just average the samples in a multisampling ADC). Since power supplies seldom have sinewave noise, it makes a difference. A Meanwell 200w supply similar to what our printers use has 150mV ripple & noise. So 24v +/- 1% +whatever noise is added by the measurement device in average or rms mode.

Then again, here's how Meanwell limits the noise they spec, which, in reality is by using quite a pi filter:

It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 19/10/2020 6:16 pm
farina
(@farina)
Eminent Member

I don't have a scope right now but I'm hoping to get one in the future. I do too many projects where it would be really useful!

Posted : 20/10/2020 1:32 am
jsw
 jsw
(@jsw)
Noble Member

Scopes are handy to have if you do any electronics work.  In today's market you can get a scope, for only a few hundred US$, that has the same specs that would be considered a laboratory grade instrument (and $$$$$$) a decade or so ago.  It's fairly reasonably for a hobbyist to get a multi-trace digital scope with digital storage and at least a couple hundred MHz of bandwidth.  The one I have has a multi-channel logic analyzer probe as well as the usual analog inputs.

Posted : 20/10/2020 2:41 am
farina
(@farina)
Eminent Member

@jsw

Yeah I funded this project ( https://www.indiegogo.com/projects/pokit-pro-multimeter-oscilloscope-logger/x/18842122#/) thinking it would be a nice hobby scope. I hope it works :). 

Posted : 20/10/2020 2:50 am
jsw
 jsw
(@jsw)
Noble Member

Interesting concept.  It looks like they are using a smartphone as the display.

Posted : 20/10/2020 3:18 am
farina
(@farina)
Eminent Member

@jsw

Yeah, I thought the concept was brilliant. Much smaller package when you need to take it somewhere. 

Posted : 20/10/2020 4:49 am
--
 -2
(@-2)
Illustrious Member

With 1MS/s they aren't going to provide anywhere near 600KHz bandwidth. Nyquist is going to eat their lunch. 250kHz will be pushing things. That is, unless they totally disregard aliasing.

ps: I own a Tek 100MHz digital scope from way back when I was working for them. I did look at one of the more recent 300MHz Chinese replicas ... not entirely impressed, but for the money a four channel 300Meg scope is a bargain these days. But probes were a soft point - nothing seemed that good.

This post was modified 1 month ago by --
It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 20/10/2020 6:17 am
farina
(@farina)
Eminent Member

@tim-m30

Yeah I don’t know it it will be great, I was just hoping for something passable and portable. 

I might end up going for something more substantial after playing with this one, but I figured I could cut my teeth with it on some of the arcade and pinball repair I do. 

Posted : 20/10/2020 6:27 am
Share:

Please Login or Register