Hey guys. I found a deal on bridge rectifiers.
These are the "looks like fork" one piece units, 8 ampers.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=160246533769
*A "dual secondaries" transformer would use 2 of those (+ -+ - ), however a "center tap" transformer uses only 1.
These are the "looks like fork" one piece units, 8 ampers.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=160246533769
*A "dual secondaries" transformer would use 2 of those (+ -+ - ), however a "center tap" transformer uses only 1.
Sneasle,
If you are using a computer sound card with 5.1 output then all you need are the amps- you are correct. No preamp, no decoder.
Most of the PC boards available are for one channel, which would allow people to buy as many as they needed for as many channels as they want. There is no problem. They probably only need to get a larger transformer and they could run them all off of one supply if desired- or as an extreme, each channel can have its own transformer and diodes.
OR a variation - the back channels sharing a power supply as they aren't as stressed usually.
If you are running them off of a soundcard probably ultimate sound quality isn't the goal so a single big supply would be most cost effective,
If you are using a computer sound card with 5.1 output then all you need are the amps- you are correct. No preamp, no decoder.
Most of the PC boards available are for one channel, which would allow people to buy as many as they needed for as many channels as they want. There is no problem. They probably only need to get a larger transformer and they could run them all off of one supply if desired- or as an extreme, each channel can have its own transformer and diodes.
OR a variation - the back channels sharing a power supply as they aren't as stressed usually.
If you are running them off of a soundcard probably ultimate sound quality isn't the goal so a single big supply would be most cost effective,
Sneasle said:
Oops! It seems that my suggestion was in error. Its not educational to use a 1 piece bridge (internally 4 diodes each).
Instead, its probably better to use discrete (individual) diodes so the class can learn the application.
Yet, you did mention using printed circuit board, so that does limit the educational value, either way.
EDIT: My suggestion was because 60 cents is better than the usual price. http://www.alliedelec.com/Search/Pr...N=KBU808&R=2660078&SEARCH=2660078&DESC=KBU808
I do not encourage abuse of the semiconductor sample program, but in your case requesting samples of semiconductors would be the best route to obtain the silicon for this project.
The reason for this is that semiconductor manufacturers want students to use their parts so that the student is familiar with the brand when they graduate. Obviously this familiarity is hoped to bring additional sales volumes when the graduate selects parts for new designs. To that end, most semiconductor manufacturers have a policy to allow students with a school email address to register and order samples (sometimes you will have to cover small shipping charges).
I built all my chipamp projects when I was a student. I was able to obtain samples for all the necessary silicon. Familiarizing yourself with the semiconductor sample process and working with vendors / sales representatives is another important lesson in the reality of product design.
After writing all that I just checked my account at National and the samples for the LM3886 chips now cost a whopping $14 apiece in shipping and handling. I don't know if students still get them for free, but you might have to call or email a local representative to see if they can send you some parts.
Regarding the rectifier diodes, any number of types will work, including the ones in your link. I would however try to place my order(s) from the fewest number of different vendors possible to save on shipping and complexity.
I'll start on a Bill of Materials tonight and see what I can find for you. For now I am assuming that you like the project enclosures that I posted a link to and that you are using the National reference schematic à la www.chipamp.com's boards. I will also consider the worst case situation that you are not able to obtain samples of the parts.
Regards,
David Malphurs
The reason for this is that semiconductor manufacturers want students to use their parts so that the student is familiar with the brand when they graduate. Obviously this familiarity is hoped to bring additional sales volumes when the graduate selects parts for new designs. To that end, most semiconductor manufacturers have a policy to allow students with a school email address to register and order samples (sometimes you will have to cover small shipping charges).
I built all my chipamp projects when I was a student. I was able to obtain samples for all the necessary silicon. Familiarizing yourself with the semiconductor sample process and working with vendors / sales representatives is another important lesson in the reality of product design.
After writing all that I just checked my account at National and the samples for the LM3886 chips now cost a whopping $14 apiece in shipping and handling. I don't know if students still get them for free, but you might have to call or email a local representative to see if they can send you some parts.
Regarding the rectifier diodes, any number of types will work, including the ones in your link. I would however try to place my order(s) from the fewest number of different vendors possible to save on shipping and complexity.
I'll start on a Bill of Materials tonight and see what I can find for you. For now I am assuming that you like the project enclosures that I posted a link to and that you are using the National reference schematic à la www.chipamp.com's boards. I will also consider the worst case situation that you are not able to obtain samples of the parts.
Regards,
David Malphurs
marchingant4 said:
Well, we won't do this as the actual project this semmester, but those of us who are 'in charge' will likely build them this semmester in order to develop the 'lesson plan' for the project.
If your still here int he spring, you can take part in it then. If not, your more then welcome to help us in the planning stages now.
No, this isn't for a class, more of a 'student program' that will happen over one semmester. Think of it like a short term SAE car team or something.
gtforme00 said:
Ya, I am very familiar with the sample process. I've samples lots of parts in the past for small projects I have worked on. For one of the student programs I am on we have to sample some of our IC's from Maxim when we need them quickly because the lead times on our small quantities are usually 5+ weeks.
And yes, because of all this sampling I am very familiar with Maxim's power management IC's and AD's accelerometers.
If all else fails, Digikey has the 3886's for $7:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=LM3886T-ND
You might want to phone and see if LM3886TF (insulated) is available.
In comparison, the LM3886T or LM3886TA is uninsulated and you'd need some Kapton (or mica) plus plastic shoulder bolts--and bolt down that circuit board so the chip doesn't slip off the insulator.
Either will need thermal compound.
Perhaps you have, or can find, 1 jar of GC Waldham Type 44? It works in the widest varieties of applications, and its economical.
In comparison, the LM3886T or LM3886TA is uninsulated and you'd need some Kapton (or mica) plus plastic shoulder bolts--and bolt down that circuit board so the chip doesn't slip off the insulator.
Either will need thermal compound.
Perhaps you have, or can find, 1 jar of GC Waldham Type 44? It works in the widest varieties of applications, and its economical.
Sneasle said:
We shall see. I've got leftover arctic silver 5
David: Have you made any more progress on that BOM? Can you send me a preliminary copy? I'd like to see what you've got.
One use of Artic Silver 5 is its "filler" feature, specific to a plastic to rough metal interface, as seen with LM3886TF onto an aluminum heatsink.
GC Waldham Type 44 is similar to Artic Ceramique, albeit at a price difference. Also, those two non-conductive compounds are areospace approved. These are much safer for LM3886T, which is non-insulated, so use an insulator, a "shoulder washer" and non-conductive paste.
Its all overkill, but I mentioned the GC because the price isn't higher than the cheap stuff, and I think that's yet one more important clue for EE students seeking application experience. Hey, don't worry, I'll be asking you guys for help with the math later.
I have a preliminary BOM written up. See attached. Shipping nearly doubles the cost of parts for a single amp order, so the more people you get in on the initial order the better.
The BOM includes the parts required to make a National reference circuit for the LM3886 (using the BOM from www.chipamp.com), plus power supply parts and terminal connections. It does not include the pc boards and associated costs.
There are several options in the power supply, depending on the desired power output and the nominal impedance of the user's speakers. For lower power applications, www.apexjr.com has a 80VA 42VCT toroid for $12.95. This should handle nearly anyones needs for 6-8 ohm nominal speakers. For higher power into 6-8 ohm loads, there is the 120VA dual 21.5V for $19.95. For full power into 8 ohms only, there is also a 100VA dual 25V toroid for $17.95. If someone is planning on trying to get full power out of the chips, you should advise them to run one transformer and power supply per chip (dual mono). If someone wants to power 4 ohm speakers, they will need to find a dual 18V or 36VCT (or lower) transformer.
Let me know what you think about the BOM.
-David
The BOM includes the parts required to make a National reference circuit for the LM3886 (using the BOM from www.chipamp.com), plus power supply parts and terminal connections. It does not include the pc boards and associated costs.
There are several options in the power supply, depending on the desired power output and the nominal impedance of the user's speakers. For lower power applications, www.apexjr.com has a 80VA 42VCT toroid for $12.95. This should handle nearly anyones needs for 6-8 ohm nominal speakers. For higher power into 6-8 ohm loads, there is the 120VA dual 21.5V for $19.95. For full power into 8 ohms only, there is also a 100VA dual 25V toroid for $17.95. If someone is planning on trying to get full power out of the chips, you should advise them to run one transformer and power supply per chip (dual mono). If someone wants to power 4 ohm speakers, they will need to find a dual 18V or 36VCT (or lower) transformer.
Let me know what you think about the BOM.
-David
You may want to add some power supply caps to that.
Here's some:
http://www.apexjr.com/capacitorsR.html#Computer
and here
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150234037892
Maybe like this:
Here's some:
http://www.apexjr.com/capacitorsR.html#Computer
and here
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150234037892
Maybe like this:
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