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Re: Which voltmeter is correct?
Stefan Trethan
On Wed, 26 Apr 2006 14:41:24 +0200, Daniel Nicoson <A6intruder@...> wrote:
yes. You can use something like the pi filter in a PC supply. basically a filter cap, then a choke coil in series, and then again a filter cap. ST |
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Re: Which voltmeter is correct?
Daniel Nicoson
I guess this brings up another issue. I imagine my car will appreciate if I
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clean up this ringing on the discharge of the SMPS. I don't imagine it will be good to let all that noise out to the rest of the car's electrical system. One more thing to learn about, low pass filters for my circuit output...That should be fun, a low pas circuit that will handle 18-21 volts DC and 20 amps. What determines whether I need a low pass or high pass or mid pass filter? Is it the fact that I want to pass low frequency current, i.e. dc output? Dan Nicoson -----Original Message-----
From: Electronics_101@... [mailto:Electronics_101@...]On Behalf Of Stefan Trethan Sent: Wednesday, April 26, 2006 3:30 AM To: Electronics_101@... Subject: Re: [Electronics_101] Which voltmeter is correct? If the meters have a peak or rectifying circuit inside instead of a averaging circuit they will pick up more of the ringing. Accuracy at higher requency is never a given. If you are unsure you could build a R/C lowpass to filter out the ringing. Check if they read zero in dc range on a ac voltage. ST On Wed, 26 Apr 2006 04:30:16 +0200, Daniel Nicoson <A6intruder@...> wrote:
Yahoo! Groups Links |
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Re: Sort of OT - Air compressors for cars that run on 12 Volts DC...
Yes and no.
As this is all in the planning stages at this point, I am not sure yet which way I will go. For the testing purposes of the machine, I could simply switch the compressor on to release the tool, then, turn the compressor off to clamp the tool. It would be very slow this way - but VERY easy to impliment - no presure switch needed, no solenoids needed, etc. However, it would not result in fast motion at all which would be bad in practical use. So, at the time of actually using the machine in the "real world", it would need an air tank and solenoid. There is another option I did not think about that might also be easy to do. I could run a pipe from the shop's compressor into the office where the machine is being prototyped. That would keep the noise outside, and would deliver regulated air. Didn't think of that till 2:30 this morning during one of my mid-night wake-ups. Chris --- In Electronics_101@..., "Stefan Trethan" <stefan_trethan@...> wrote: are you not?of tool
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Re: AVR programmer question
Stefan Trethan
I just want to let you know i found a workaround for that.
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I checked the otuput pins of the LPT and found pin 9 (data 7) is low in "idle" while for example pin 8 (data6) is high. So i simply moved the reset signal to this pin and now the programmer works normal again as it should without disconnecting the programmer for testing... I have no idea whatsoever how the PC decides what state the data lines are left in when idle. I'm quite certain it worked before on the old configuration, so it must have changed somehow. I just hope it doesn't change again. Seems like one of these things that just happen and there's no finding out how or why... Anyway, this whole story had one good result, i now have dug out the switch box and can plug it up to switch between programmer and printer without having to change the plugs... Still strange... ST On Mon, 24 Apr 2006 19:15:39 +0200, Stefan Trethan <stefan_trethan@...> wrote:
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Re: Low & high current switch
No,its current withstanding capacity of the contacts. Regards, Anita Kuber????????????????????????????????????????????????? ?
----- Original Message -----
From: Anita.Kuber@... To: Electronics_101@... Sent: Wednesday, April 26, 2006 8:12 AM Subject: [Electronics_101] Low & high current switch Hello ?Everybody, In one of the project ?I am using high current switches. But my question is how to identify high and low current switches? Please help me in this regard. ? Do you mean high-side and low-side switching? ? Leon -- Leon Heller, G1HSM leon.heller@... YAHOO! GROUPS LINKS
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Re: Low & high current switch
Leon Heller
¿ªÔÆÌåÓý
Do you mean high-side and low-side
switching?
?
Leon
--
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Re: Sort of OT - Air compressors for cars that run on 12 Volts DC...
Stefan Trethan
But you are using a air tank and a magnetic valve to operate ram, are you not?
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ST On Tue, 25 Apr 2006 23:34:57 +0200, lcdpublishing <lcdpublishing@...> wrote:
Oh man I hope it doesn't have a plastic piston! At 300 PSI, that |
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Re: Which voltmeter is correct?
Stefan Trethan
If the meters have a peak or rectifying circuit inside instead of a averaging circuit they will pick up more of the ringing.
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Accuracy at higher requency is never a given. If you are unsure you could build a R/C lowpass to filter out the ringing. Check if they read zero in dc range on a ac voltage. ST On Wed, 26 Apr 2006 04:30:16 +0200, Daniel Nicoson <A6intruder@...> wrote:
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Low & high current switch
Hello ?Everybody, In one of the project ?I am using high current switches. But my question is how to identify high and low current switches? Please help me in this regard. Regards, Anita Kuber????????????????????????????????????????????????? Executive Engineering?????????????????????????????????????? ??????????? E-mail: anita.kuber@... |
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Which voltmeter is correct?
Daniel Nicoson
Working on my SMPS circuit tonight. This past weekend I fully instrumented
the circuit with 4 digital voltmeters. I have two that are exactly the same, cheap Chinese DVM's that appear to give consistent data. I am using those two to measure the voltage on the input shunt and the output shunt. This way I know how much current is coming in and out. Problem began tonight when I couldn't get the output voltage down to 18 volts as it should be. Finally it clicked that the input current was only 60% of what it should be. Used the fourth DVM to check the output voltage. Big difference. So I changed batteries in both of the two voltmeters that couldn't agree. That brought the voltage difference down to just about .4 volts difference. Next, I grabbed a 9 volt battery and put them both on at the same time. Better, only a .04 volt difference. So they agree on pure DC. They must process noisy voltage differently. So I put them both back on the discharge voltage position of the circuit and put the oscilloscope probes on too. The meters don't agree by the same .4 volts. The scope shows that there is no real ripple on the output (this is a two-phase SMPS so it does have much lower ripple, plus my discharge cap is oversized by a factor of three). The scope does show some significant "ringing" where the mosfets turn on & off. At the 5uS setting there is no real area under the ringing trace. Amazingly, I did not carefully read what the oscilloscope thought was the correct voltage...Not sure why. In this case it would probably be the most accurate indication of voltage... So my guess is one of the DVM's can tolerate the ringing and one can't? Extreme accuracy is not a huge concern for this part of the project. I would like to be within .1volt on all my meters for this purpose. I am currently trying to get the feedback loop tuned. Actual output calibration will be something I worry about later on. Thoughts? Dan Nicoson |
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Re: newbie
John Popelish
--- In Electronics_101@..., "wombat_eagle" <wombatt@...>
wrote:
I just uploaded to the files section (Popelish folder) a simpleWhat I'd like to find right now is a simple PWM circuit using either schematic for a circuit that uses mostly dirt common parts and converts a DC control voltage to PWM output for a small DC motor. The only unusual part is the output switching transistor, which is a high current, high gain device in a small package. It runs about $9 for 10 pieces from Digikey. Here is the data sheet: The LM393 is a dual comparator with an open collector output. You probably want the P or N suffis part, for a through hole (or socketable) part. The B section is a triangle wave generator and the A section compares this to the DC control voltage, and turns the PWM on any time the control voltage is more positive than the triangle. |
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Re: Sort of OT - Air compressors for cars that run on 12 Volts DC...
Daniel Nicoson
¿ªÔÆÌåÓýProblem with vacuum is now you are only working with at best a 15 psi pressure differential.? He started the problem by stating he needs about 100 psi to make things work. ? I like the several gallon pressure tank.? Fill it from your garage air compressor as you start your work session (assuming you have one), it will probably last the full work session. ? Only other possibility is that some of the higher end cars use air suspensions that adjust for load etc.? I¡¯m sure one of these pumps would probably get your 100 psi and be fairly reliable.? They would only be cheap if you could get one from a junkyard for low $$.? I¡¯m sure they cost several hundred dollars to buy new or rebuilt. ? Good luck with the project. ? Dan Nicoson ? -----Original
Message----- ? I have one too, I wouldn't consider using it in the shop, I would consider it a toy, marginal at that. ? When in doubt, turn the page upside down and look at the drawing again.? :D? Vacuum could be an alternative;? springloading the air ram, and 'emptying' it for action.? I have a vacuum pump, it's the size of a car battery, can pull a lot, not very noisy, one drawback, not cheap. ? Just thought I'd throw that in, in case you have one on hand.? You need a spring with compressed air to push the air ram back anyways, it's not like you need extra parts. ? Robert :) ? -----Message d'origine-----
De?: Electronics_101@... [mailto:Electronics_101@...] De la part de Bruce ·¡²Ô±¹´Ç²â¨¦?: avril 25 2006 19:01 ??: Electronics_101@... Objet?: Re: [Electronics_101] Re: Sort of OT - Air compressors for cars that run on 12 Volts DC... I have a couple of
them.?? Down right handy when you have a flat.??? ? |
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Re: Sort of OT - Air compressors for cars that run on 12 Volts DC...
¿ªÔÆÌåÓýDouble action cylinders, vacuum or pressure, doesn't
matter.
Just a matter of which port gets the
connection.
?
You can get 80$r compressors easily thru Harbor Freight and
Big Lots.
usually 4 gallon tank, 125 max psi, 5.2cfm? @
90psi.
about the size of 2 milk crates.
I use one for trade shows, works great for 1-2 hours,
before needed a cooling cycle.
?
Or you could pressurize a portable tank to 120 and use that
as a source, you don't need an enormous volume of air, this should last you
quite some time at 11 gallons.
That would be less than 40$
?
Gory
Corey Look for MinionsWeb at The Great Lakes Fright Fest -
coming up fast June 2-4 2006! ?IronStock ? ? From: Electronics_101@... [mailto:Electronics_101@...] On Behalf Of Robert Hedan Sent: Tuesday, April 25, 2006 9:16 PM To: Electronics_101@... Subject: [Electronics_101] Re: Sort of OT - Air compressors for cars that run on 12 Volts DC... I have
one too, I wouldn't consider using it in the shop, I would consider it a toy,
marginal at that.
?
When
in doubt, turn the page upside down and look at the drawing again.?
:D? Vacuum could be an alternative;? springloading the air
ram, and 'emptying' it for action.? I have a vacuum pump, it's the size of
a car battery, can pull a lot, not very noisy, one drawback, not
cheap.
?
Just
thought I'd throw that in, in case you have one on hand.? You need a spring
with compressed air to push the air ram back anyways, it's not like you need
extra parts.
?
Robert
:)
?
-- |
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Re: Sort of OT - Air compressors for cars that run on 12 Volts DC...
¿ªÔÆÌåÓýI have
one too, I wouldn't consider using it in the shop, I would consider it a toy,
marginal at that.
?
When
in doubt, turn the page upside down and look at the drawing again.?
:D? Vacuum could be an alternative;? springloading the air
ram, and 'emptying' it for action.? I have a vacuum pump, it's the size of
a car battery, can pull a lot, not very noisy, one drawback, not
cheap.
?
Just
thought I'd throw that in, in case you have one on hand.? You need a spring
with compressed air to push the air ram back anyways, it's not like you need
extra parts.
?
Robert
:)
?
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Re: newbie
signal snatcher
PWM can be created using a comparator. This is the
recipe for PWM for voice or data transmission: The clock signal is transformed to a triangular wave and fed into the comparator terminal that usually provides the reference voltage. The baseband signal is fed into the other terminal. The result is a PWM signal at the output. For motor control or power supplies, there are a number of ICs that will do the job for you. The TL494 is available in SMD format from <>. signalsnatcher Current location - Wollongong, the steel city, Australia Specialising in - improvised communication networks, cabled and wireless data transmission, telemetry, remote control and associated technologies. Send instant messages to your online friends |
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Re: Sort of OT - Air compressors for cars that run on 12 Volts DC...
Bruce
¿ªÔÆÌåÓýI have a couple of them.?? Down right handy when you have a flat.???Mine has a pot metal piston, as is the cylinder.?? If you get 300 PSI's out of it, then I would really be surprise.?? I don't remember how much mine is rated for, but once it gets past 50 - 60 psi, it really starts lugging.?? I doubt it would get past 100 psi.? And if it did, it would have to run a lot longer than the 15 min it's rated for.? Bruce ?? lcdpublishing wrote: Oh man I hope it doesn't have a plastic piston!? At 300 PSI, that |
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Re: Sort of OT - Air compressors for cars that run on 12 Volts DC...
Roy J. Tellason
On Tuesday 25 April 2006 05:04 pm, lcdpublishing wrote:
So, I was thinking about using one of those tiny air compressorsI have one. It's noisy, even outdoors. The air hose is very short. And the paperwork that came with it said that it shouldn't be run for more than about 15 minutes straight, or it would get too hot, and it does tend to get kinda hot... Not recommended. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin |
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Re: Sort of OT - Air compressors for cars that run on 12 Volts DC...
Oh man I hope it doesn't have a plastic piston! At 300 PSI, that
would be downright scary to use! I don't suspect these things are engineered to last for hundreds of hours of use, but if I can get it to last a couple of hours, that would probably be all that is needed for a couple of years of machine use. The air cylinder won't take that much volume to actuate and it only needs to run long enough for a tool change - long enough to actuate the piston to release the collet. Springs (bellevile) will be used to hold the collet closed. So, I am guessing the compressor might run for 5~ 10 seconds or so per tool change. I don't know how much volume they produce, I wouldn't expect much so 5 ~ 10 seconds is a W.A.G. Chris --- In Electronics_101@..., "Stefan Trethan" <stefan_trethan@...> wrote: plastic pistons.time ago.power. the working air in
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Re: Sort of OT - Air compressors for cars that run on 12 Volts DC...
Stefan Trethan
Well, the cheap ones can't be great quality, i think they have plastic pistons.
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I even saw a webpage of some guy rebuilding one for quality a long time ago. As i said before i use a fridge compressor, but that is mains power. ST On Tue, 25 Apr 2006 23:04:57 +0200, lcdpublishing <lcdpublishing@...> wrote:
Hi guys, |
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Sort of OT - Air compressors for cars that run on 12 Volts DC...
Hi guys,
This one is a bit O.T. sort of. I am working on my mini-mill project (which is very much electronics) and when I get stuck on the electronics and need to dwell and think a bit, I go back to working on the mechanics. So, I am pondering the application of an automatic tool changer (Thanks Robert :-)) on this little machine. I will be needing air presure - around 100 PSI to drive an air cylinder. I have a big compressor in the shop, but I am working on this little machine in the house (and plan on keeping it in there too if I can). So, I was thinking about using one of those tiny air compressors that people buy for their cars. They have the cigarette lighter adapters and run on 12 Volts. Some of the ones I am seeing claim they can generate up to 300 PSI (about 10 times more than the average car tire ever needs). I am just wondering if any of you guys have one of these little things and if they work okay? Thanks and sorry for the sidetrack! Chris |
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