yes, the circuits can be modified to work with 12V relay. I recommend that.
But, the original circuit is flawed.
Add a series resistor to feed the relay and switching transistor. Then add that extra Capacitor as described for snap actuation of the relay. This resistor will run hot (about 3times the dissipation as the relay coil) so make it big enough (or a few in parallel) to dissipate the heat reliably.
The 10V or 12V transformers will probably give around 18Vdc to 24Vdc and would be perfect for a resistor + relay.
Ashok,
could you post a diagram with the modification showing the extra R & C for a 12V relay.
Having built many of these DC protect ccts I can attest to the relay closing quite convincingly. I guess it's due to the mechanical nature of the relay. I.e. when the voltage is high enough to actually move the armature from it's rest position, it's plenty high enough to secure a solid click when the armature strikes the pole face. Remember the voltage is still rising as the armature accelerates towards the pole face.
The more important factor is the release time. In this case with a DC offset of 20v, Q5 removes power from the relay within 6 mS. It is this time that is more important in terms of "snap" so that the mechanical return spring of the relay is completely unopposed. Of course this time is even less with the more common fault of the full DC rail on the output.
Regarding the use of a 12 volt relay, this is easily done. Either by inserting a series resistor to drop the voltage or by using a 12 volt power supply (13-14 volts is ok). In case of the latter the relay closing time when first powered up will be longer. If this is not desired then the timing capacitor can be reduced in value.
Cheers
Q
The more important factor is the release time. In this case with a DC offset of 20v, Q5 removes power from the relay within 6 mS. It is this time that is more important in terms of "snap" so that the mechanical return spring of the relay is completely unopposed. Of course this time is even less with the more common fault of the full DC rail on the output.
Regarding the use of a 12 volt relay, this is easily done. Either by inserting a series resistor to drop the voltage or by using a 12 volt power supply (13-14 volts is ok). In case of the latter the relay closing time when first powered up will be longer. If this is not desired then the timing capacitor can be reduced in value.
Cheers
Q
Hi Guys,
I took the liberty of making some mods on Quasi's circuit , as suggested by Andrew and the need to use a 55V dc supply and 12 volt relay.
Check out the circuit and its response. Switch on delay is close to 4 seconds. Trigger with a +/- 5 volt fault is about half a second.
Q1 , Q2 ………………… BC547B
Q3 ………………… BC557B
Q4 ………………… BC 640
Q5 ………………… BC 546B
All resistors ¼ watt except :
R9 …( 6 watt will run quite hot ) … 10 watt
R12 ……………………………….. 2 watts
RL is a 12 V relay ………Typically 280 ohms to 300 ohms
D1 …………………… 1N4002
C3 ……………………. 470u / 16 V
C4 …………………….. 47u / 63 V
C1 ………………… .NP 22uF / 50V or made up using 2x 47uF / 50V Electrolytic
C2 …………………. NP 22uF / 16 V or made up using 2x 47uF / 16V Electrolytic
DC supply = + 55V dc.
The graph shows the voltage across the relay coil . The high voltage of close to 25 volts dies down in less than 60m seconds. Small relays operate in about 10 to 20 milli seconds. Larger ones might take a bit more time -- 40 mS ? Continuous dc on the relay is just under 10 volts.
The dc offset is applied at 5 sec and so you can see about half a second delay in turning off.
You could try without C4 but C3 is essential.
Without C4 the coil will have no turn on spike . In that case R12 can be changed to 1K ohm 6 watts and R9 can be removed .
R6 could be raised to about 82k to cut down on dissipation.
C1 and C2 can easily be made up with two electrolytic capacitors connected in series . Tie the - ve terminals together and use the other two terminals .
I took the liberty of making some mods on Quasi's circuit , as suggested by Andrew and the need to use a 55V dc supply and 12 volt relay.
Check out the circuit and its response. Switch on delay is close to 4 seconds. Trigger with a +/- 5 volt fault is about half a second.
Q1 , Q2 ………………… BC547B
Q3 ………………… BC557B
Q4 ………………… BC 640
Q5 ………………… BC 546B
All resistors ¼ watt except :
R9 …( 6 watt will run quite hot ) … 10 watt
R12 ……………………………….. 2 watts
RL is a 12 V relay ………Typically 280 ohms to 300 ohms
D1 …………………… 1N4002
C3 ……………………. 470u / 16 V
C4 …………………….. 47u / 63 V
C1 ………………… .NP 22uF / 50V or made up using 2x 47uF / 50V Electrolytic
C2 …………………. NP 22uF / 16 V or made up using 2x 47uF / 16V Electrolytic
DC supply = + 55V dc.
The graph shows the voltage across the relay coil . The high voltage of close to 25 volts dies down in less than 60m seconds. Small relays operate in about 10 to 20 milli seconds. Larger ones might take a bit more time -- 40 mS ? Continuous dc on the relay is just under 10 volts.
The dc offset is applied at 5 sec and so you can see about half a second delay in turning off.
You could try without C4 but C3 is essential.
Without C4 the coil will have no turn on spike . In that case R12 can be changed to 1K ohm 6 watts and R9 can be removed .
R6 could be raised to about 82k to cut down on dissipation.
C1 and C2 can easily be made up with two electrolytic capacitors connected in series . Tie the - ve terminals together and use the other two terminals .
Attachments
Hi folks,
I have setup a basic web page as a document access facility, plus some other stuff. In the main it is there to reduce the need for people to read the entire thread (although there is value in doing so) and to access information more easily. The site is by no means finished, but I have published some of the stuff covered in this thread.
Ok.......amplifier designer I am...web designer I'm not, so please understand this when you visit.
http://www.adam.com.au/cgpap/QuasiWeb/index.htm
Cheers
Quasi (not a web page designer)
I have setup a basic web page as a document access facility, plus some other stuff. In the main it is there to reduce the need for people to read the entire thread (although there is value in doing so) and to access information more easily. The site is by no means finished, but I have published some of the stuff covered in this thread.
Ok.......amplifier designer I am...web designer I'm not, so please understand this when you visit.
http://www.adam.com.au/cgpap/QuasiWeb/index.htm
Cheers
Quasi (not a web page designer)
Well, i did noticed that relay closing time is longer with 12 volts. I didn't reduce cap, i have reduced the R from 330k to some 220k-150k and it works fine. This all i made on original quasis design.
I did try puting resistor in series with rely but i dodn't like that kind aproach.
I tought allso that even other resistors have to change for 12 volt design.
I did try puting resistor in series with rely but i dodn't like that kind aproach.
I tought allso that even other resistors have to change for 12 volt design.
ashok said:
quasi said:
Ashok,
Thanks for all your efforts. All I had asked about was the dimensioning of the relay others had used. Great the DC Protection has had some refinement and discussion by those of the last week or so. Sorry it opened up a big discussion when all I wanted to know was if I had found a suitable relay.
What is "All resistors ¼ watt"?
Is a new PCB for the module and the seperate DC Protection PCB required or is this just a change in part values?
quasi,
I am still swamped with some crisis here. That said I know you have a PDF guide for your nmos amps. Would it be helpful to place it on your quasi audio web page? When I have a chance to update the site I created about 2 years ago maybe it would be helpful to place the link to there are well. I am not sure, as my assumption of placing links to key posts of the thread seems to not hold after an unknown time. They do hold for a period of time. I know as I checked them from time to time for various reasons. That was one of the major reason for the site I created. I tried to update the site about a year ago, but it was plagued with site software administration related bugs the hosting company has not sorted out yet.
Sadly external links to diyAudio posts become invalid at some point. I suspect the software of diyAudio changes the link reference points for reasons and events unknown, but within the diyAudio site the site manages to keep these direct to posting link references changes updated. Sad as I had initially started to do the "links" collection externally only to find after a few months the direct posting links started to fail. Maybe one of the moderators can bring this shortfall to the attention of the software folks to have the direct posting links stabilized to allow for external posting links. Any moderators listening that have influence on the software developers?
Any idea how your page, the links collection I have made, et al can be communicated so the same repeat questions do not arise? I know yourself, others and myself have answered the same most frequent questions about current schematic, current PCB, module setup, basic PSU dimensioning even if it is to point out the related posting or your having to eMail the your guide document. I know you cannot post the guide document as it exceeds the diyAudio posting size limit. Ergo why maybe at least having the guide on your newly created web page might be helpful. The only issue that remains is how to ensure people know about the site as it will also fade as a posting that others will not find as they will not read through the thread to find the reference. Maybe the software diyAudio uses needs an ehancement for a thread "reference" where we can place links to external web sites like yours and also allow a links collection to exist as well. Any moderators listening that have influence on the software developers?
I know I have at least a few PCB board variations to post. I also still want to create a super guide that takes much of the thread information and organize and index it in a document. The software I was using that had some serious challenges in the size of the PDF it created has improved greatly not only to reduce the PDF size, but makes it so easy to create PDF bookmarks to allow easy navigation of the PDF for the information one would look for. Now all I need is time. lol lol The links collection indirectly is part of that document creation process, so the links collection I have done and still to do/update has a longer term purpose and goal. Actually I think now rather than one superguide I would have different guides, one specificallay for the quasi amps (includes parts and rail varients and any related calculations), then PSU, DC Protection, softstart, SOA, matching, et al each in a seperate document. The idea is certain elements are not the amplifier itself and common to any similar amplifier. Does the dividing out the related design elements make sense while still being a collection of what is helpful information for building the quasi amplifiers?
All,
I will get to the links collection just the same to update the current project for building and the amp specifications. I just do not have the time to do so yet. I just ask for all to be patient with my situation.
Regards,
John L. Males
Willowdale, Ontario
Canada
21 May 2007 11:58
21 May 2007 12:02 Ommitted question re resistor wattage. jlm
(Unofficial Thread Researcher and frequent thread ghost of more than year)
".........What is "All resistors ¼ watt except :".............."
OK that sentence was not properly completed but I thought the meaning was obvious.
It meant " all resistors 1/4 watt except the following resistors .
I have mentioned those resistors with their values.
I modified the circuit to accept a +55 volt dc supply. I added a couple of resistors and a capacitor . The main circuit is the same.
To avoid adding additional parts , it's better to adapt the parts values ( if required ) for 12 volt operation ( and use an extra 12 volt supply ). You could drop 55 volts to 12 volts .
It's good to mention things that open up new discussion. It will make the operation of the present circuit clearer and improve it by component value or configuration or even evolve into newer forms. The others can then pick and choose what they wish to use. Discussion and debate is a very healthy thing for the forum.
Never apologise for starting a big discussion or debate........it's just what the forum wants ...............I think!
All we might want is that people keep flame throwers and ego's
locked away in the closet.
Cheers.
OK that sentence was not properly completed but I thought the meaning was obvious.
It meant " all resistors 1/4 watt except the following resistors .
I have mentioned those resistors with their values.
I modified the circuit to accept a +55 volt dc supply. I added a couple of resistors and a capacitor . The main circuit is the same.
To avoid adding additional parts , it's better to adapt the parts values ( if required ) for 12 volt operation ( and use an extra 12 volt supply ). You could drop 55 volts to 12 volts .
It's good to mention things that open up new discussion. It will make the operation of the present circuit clearer and improve it by component value or configuration or even evolve into newer forms. The others can then pick and choose what they wish to use. Discussion and debate is a very healthy thing for the forum.
Never apologise for starting a big discussion or debate........it's just what the forum wants ...............I think!
All we might want is that people keep flame throwers and ego's
locked away in the closet.
Cheers.
Hi Quasi,
Don't forget to include your other high powered design.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=53264&perpage=10&pagenumber=33
Looks like you'll have everything to offer from your web site from small to big amps.
I'd like pcbs too
Don't forget to include your other high powered design.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=53264&perpage=10&pagenumber=33
Looks like you'll have everything to offer from your web site from small to big amps.
I'd like pcbs too
smokingmachine said:hellow!
how can i print the nmos500 layout that it will be the right size?
I will do 2 channel amplifier with n-mos500(500rms at 4 ohm) and 2 boxes with b&c speakers drivers inside
when i am done, i will post pictures of the amp and i hope i will be sattisfied with this amp
SmokingMachine,
The PCB images ae in a PDF document. What this means is the PCB will print the correct and actual size to any printer configured correctly for your system using actual page size printer options (normal setting). If you have a special printer setting to enlarge or decrease a print page for the printer than you will need to set it to normal. this will not likely be requred for most users. Those that will need to change already know the details and how to.
Regards,
John L. Males
Willowdale, Ontario
Canada
23 May 2007 22:21
(Unofficial quasi Thread Researcher)
smokingmachine said:
Smokingmachine,
IRF240 or IRFP240? Latter is a TO-3 device and former is a TO-247 device. They have very different power and specifications.
"Better is a relative term" depending on your you power requirements and the speaker load.
The "more current" and "smaller "power disapation" rating are two of a few of the specifications used to determine a device SOA. SOA is a rather complex to determine as it is a function of device temperature handling characterists, voltage rating, operating temperature, heat sinking, signal characteristics, operating level of the amplifier, load phase angle, to name just a few.
The NMOS200 PCB is available in two "flavours" a single pair of TO-247 devices or 2 paor of TO-220 devices. If you need two or more TO-247 devices then the NMOS350 or NMOS500 will be what you will need.
Regards,
John L. Males
Willowdale, Ontario
Canada
23 May 2007 22:41
keypunch said:
Thanks John.
After careful and considered assessment of all likely candidates, I would like to offer you the role of OQTR (Official Quasi Thread Researcher). I am also pleased to inform you that all of your current benefits, conditions and remuneration will be retained without change.
Good Luck in your new role
Sincerely
Quasi