Hi all, it turns out that the PSU measures quite OK too. I lack the time to be active on this project and I am slightly doubting a GB is possible considering the numbers so please prove me wrong 
Would you like a GB consisting of a board and Rcore transformer (EUROPE ONLY) ? IMO the design works more than OK but you will have to accept it like it is. I made a few small changes after testing.
Let's say that if there is enough demand I wil consider making it a GB. Contrary to the DAC we made this will be a one time only GB. So I hope members will receive this info in time and I hope one of you can make a Google spreadsheet It will be one run so being too late is just being too late.
PS it can be changed to other voltages too but that will be your own thing. Just changing the setting resistors and adapting to parts that are rated for more than the desired output voltage and you're done. With the BOM parts you can go to 12 V output voltage by changing the resistors and using a different transformer. As this is an LDO design carefully choosing a transformer is recommended.
Would you like a GB consisting of a board and Rcore transformer (EUROPE ONLY) ? IMO the design works more than OK but you will have to accept it like it is. I made a few small changes after testing. Let's say that if there is enough demand I wil consider making it a GB. Contrary to the DAC we made this will be a one time only GB. So I hope members will receive this info in time and I hope one of you can make a Google spreadsheet
It will be one run so being too late is just being too late. PS it can be changed to other voltages too but that will be your own thing. Just changing the setting resistors and adapting to parts that are rated for more than the desired output voltage and you're done. With the BOM parts you can go to 12 V output voltage by changing the resistors and using a different transformer. As this is an LDO design carefully choosing a transformer is recommended.
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Guess i have been too quick with my replies, as the hint for the spreadsheet did not exist when i did post
So yes, i will better use that one.
As said before: careful selection of the right transformer is mandatory to keep low heat emission and efficiency right. Do yourself and me a favor, don't think you have a leftover transformer that will work... The SBT PSU should be able to work with a 5V 3A transformer but that is not an industry standard value for most transformer manufacturers AFAIK. I will deliver an industrial quality 6V Rcore transformer to European members that want one and that are willing the to pay the price and shipping costs (hear, hear, here is a "vendor" speaking). The 6V 3A Rcore transformer is relatively small, it is virtually silent and it has a very low stray field. For 5V output one should not exceed 6V AC.
@ overseas members: just buy the right specced transformer and support your local industry at the same time
@ overseas members: just buy the right specced transformer and support your local industry at the same time
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Joined 2006
For science's sake I just measured the temperatures of the SBT PSU. I used a prototype with an SBT + a USB WD Elements 500 gb harddisk as a load. The lid of the case was off and both sides were covered by metal sheets with no ventilation slots just to make the situation less optimal (as the top cover was removed for doing the measurements). The 6V Rcore transformer was used here. I left the harddisk idling. Ambient temperature was 21,1 degrees Celsius, the chips tab was 42,3 degrees Celsius and the heatsink was 44,8 degrees Celsius max. after playing internet radio for half an hour. The Rcore transformer was 28 degrees max. and the large filter cap was 27 degrees Celsius. Output voltage was 4,943 V. Connecting the harddisk caused a 0,003 V decrease
Heatsink used is the SK129 50,8 mm which is the BOM type. For those that will use large/high cases a 60,3 mm SK129 is possible. The cooler the better.
Heatsink used is the SK129 50,8 mm which is the BOM type. For those that will use large/high cases a 60,3 mm SK129 is possible. The cooler the better.
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Forgot to mention that just the Squeezebox Touch playing leaves the heatsink at 34,2 degrees Celsius (38 when both sides are closed with metal sheets). That's 93.56 Fahrenheit (100.4 when the sides are covered with metal sheets) for those that not adhere to international standards
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Great Project Jean-Paul. I would love to participate, but I respect your request for Europe only. If you go ahead and are willing to send to the US, then count me in. I would even go for a board an no R-core with me taking the responsibility to source an appropriate transformer.
Alternatively, if the GB doesn't make sense, would you be willing to share the gerber files and BOM? Naturally, I would repect your design and authorship.
Keep up the interesting work.
Jac
Alternatively, if the GB doesn't make sense, would you be willing to share the gerber files and BOM? Naturally, I would repect your design and authorship.
Keep up the interesting work.
Jac
My partner in Group Buys is Subbu. Subbu is located in the US and he will distribute the boards there. We agreed on this today. No transformers though but finding a 5V 3A transformer in the USA is simple. It seems that Triad Magnetics VPS10-2500 is a good one (it is able to deliver 5A which won't harm), at least that one is used by John Swenson in his PSU. I don't know as I haven't tried it. It is very cheap and it has good specifications. Too bad it can only be found at Mouser here which charges 20 Euro for shipping a 10 Euro transformer. IMO I should first try one myself before endorsing it to others but I will have to order 7 pieces to avoid the shipping costs. Send me one and you'll have some boards for free
I attached a picture of the measured prototype. It is hard to see but it is quite compact. I had this case and wanted to use it so careful positioning of the parts was necessary. Please note the retro (but not connected) Ampere-meter. I don't want the added resistance at the output, maybe I will provide for a connector block before the regulator.
I attached a picture of the measured prototype. It is hard to see but it is quite compact. I had this case and wanted to use it so careful positioning of the parts was necessary. Please note the retro (but not connected) Ampere-meter. I don't want the added resistance at the output, maybe I will provide for a connector block before the regulator.
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Connector for an Ampere-meter has been added (before the reg).It seems most like the analog meter, those that won't use one need to solder a jumper wire. The power LED can be built in the meter (instead of the light bulb that most have) in any color you like. Just an idea. It saves from drilling a hole for the LED and an illuminated meter looks good.
The Triad VPS10-2500 does look very good. I have also had luck with smaller Antek toroids. Something like the Antek AS-0505 (50 VA, 5V) might be a possibility, although I don't see any dimensions, so it could be big.
Yes I want one VPS10-2500 for testing. Thankfully it has 230 V primaries as well.
It appears that heat is a major consideration, so if the PCB is not yet in production, can I make a suggestion: maybe rearrange the board so that the LT1764 is located at the very edge - that way we can choose to use an external heatsink.
Not necessary, please see the measurements in post #49. It is all about thinking from the start to keep heat emission low. Other way of designing. If losses can be kept low heat emission will be low.
There is absolutely no sense in turning energy in useless/excess heat just to have the freedom to use a wrong transformer and to be rewarded with the need for large chunks of aluminium IMHO
Thanks.
There is absolutely no sense in turning energy in useless/excess heat just to have the freedom to use a wrong transformer and to be rewarded with the need for large chunks of aluminium IMHO
Thread now residing in Group Buys.
Thanks.
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