Hi folks,
I'm finishing a pcb-layout for a voltage regulated psu-board for dual rails (like +/-35V) which uses the LT1083/LT1084/LT1085 regulator (the high power (7 A) TO-3P variant) for both polarities. I'm going to power my power amp with it.
It is very small in size, currently 50x70mm, double sided, has very fat tracks (150mills for the regulated side), has well separated tracks (20mills average track clearance) and will be manufactured with heavy copper (70um).
One board gives both voltages (adjustable from +/-1.25V up).
This is the first time I'll order at this boardhouse, but I've heared the board edges are cut - not milled - so probably don't look that perfect as you're used to. However this does not have an impact on functionality (just looks).
Big advantage - they're cheap.
Cost depends on number of boards, rough guess is about 18 Euros per board for 4 pcs (that I need), of course dropping with every board that comes in addition.
I'm looking if there's interest, so we could order more boards and benefit from a lower price.
Have fun, Hannes
PS: I will post schematic and layout in the next few days.
I'm finishing a pcb-layout for a voltage regulated psu-board for dual rails (like +/-35V) which uses the LT1083/LT1084/LT1085 regulator (the high power (7 A) TO-3P variant) for both polarities. I'm going to power my power amp with it.
It is very small in size, currently 50x70mm, double sided, has very fat tracks (150mills for the regulated side), has well separated tracks (20mills average track clearance) and will be manufactured with heavy copper (70um).
One board gives both voltages (adjustable from +/-1.25V up).
This is the first time I'll order at this boardhouse, but I've heared the board edges are cut - not milled - so probably don't look that perfect as you're used to. However this does not have an impact on functionality (just looks).
Big advantage - they're cheap.
Cost depends on number of boards, rough guess is about 18 Euros per board for 4 pcs (that I need), of course dropping with every board that comes in addition.
I'm looking if there's interest, so we could order more boards and benefit from a lower price.
Have fun, Hannes
PS: I will post schematic and layout in the next few days.
Board
To be able to choose a suitable heatsink depending on the load, I think it's most comfortable to use an external heatsink, off-board to be flexible. So you can use something small for your preamp, but a real chunk of alu (1-2 K/W) for your power amp.
To be able to use thick or multiple cables I used the dual Molex-connectors in parallel for the outputs, so to get lowest resistance. For the ground connection I use a soldered connection.
Maybe some cosmetic changes are left to be done, but otherwise that's it.
I'm happy about every comment on improving it further!
Feel free to mail me directly if you're interested (or post here).
Have fun, Hannes
To be able to choose a suitable heatsink depending on the load, I think it's most comfortable to use an external heatsink, off-board to be flexible. So you can use something small for your preamp, but a real chunk of alu (1-2 K/W) for your power amp.
To be able to use thick or multiple cables I used the dual Molex-connectors in parallel for the outputs, so to get lowest resistance. For the ground connection I use a soldered connection.
Maybe some cosmetic changes are left to be done, but otherwise that's it.
I'm happy about every comment on improving it further!
Feel free to mail me directly if you're interested (or post here).
Have fun, Hannes
Attachments
Hi agent.5,
yes I've considered all your points; the diodes are not necessary for this regulator as it has an internal diode (capable of handling microsurge currents of 50A to 100A!). You can check this in the datasheet
2 reasons I didn't add a Vout cap: first this cap should be close to the load, preferable without parasitic wire resistance in between. 2nd there's simply no space! The size is fixed and you can see there's simply no space left! I would also have added the option for using the dual as 2 single rails, but same story.
If you're still interested, just let me know!
Have fun, Hannes
yes I've considered all your points; the diodes are not necessary for this regulator as it has an internal diode (capable of handling microsurge currents of 50A to 100A!). You can check this in the datasheet
2 reasons I didn't add a Vout cap: first this cap should be close to the load, preferable without parasitic wire resistance in between. 2nd there's simply no space! The size is fixed and you can see there's simply no space left! I would also have added the option for using the dual as 2 single rails, but same story.
If you're still interested, just let me know!
Have fun, Hannes
If you read the datasheet you'll need a minimum required capactiance _close_ to the regulator. I can read 10 uF tanalum but in your case I would choose 10-100 nF/63 V polyester/ceramic plus 10-22 uF 63 V electrolytic cap.
Hi P-A!
Of course! That's the reason I use 2x 15A molex connectors in parallel for the outputs, to get the parasitic resistance to a minimum. Mentally I just add the cabling to the ESR of the cap, which is higher than some centimeters of wire anyway.
From reading the datasheet it is for me unclear why you want to use a bypass, since a 22uF Tantalum or 150uF elco gives perfect stability (as the datasheet says under all conditions). AFAIK Elcos have a rather weak high frequency response, so depending on the regulator this could be needed.
Maybe you could give me a hint on this?
Thank you very much, Hannes
Of course! That's the reason I use 2x 15A molex connectors in parallel for the outputs, to get the parasitic resistance to a minimum. Mentally I just add the cabling to the ESR of the cap, which is higher than some centimeters of wire anyway.
From reading the datasheet it is for me unclear why you want to use a bypass, since a 22uF Tantalum or 150uF elco gives perfect stability (as the datasheet says under all conditions). AFAIK Elcos have a rather weak high frequency response, so depending on the regulator this could be needed.
Maybe you could give me a hint on this?
Thank you very much, Hannes
Hi SheldonD, sorry for my late reply, I've been busy!
From a quick look you can use the lm338 also; they have the same pinout. However you would need to bend the leads a bit, since it's a different package (TO-220 vs TO-3P of the LT1083). I will see if you can add some additional pads to the board, but don't get too excited, there's only little space.
Acutally I don't know exact price breaks as I didn't plan for a real large-scale group buy. I need some boards for myself and thought that maybe others would needs some as well, since that kind of regulator boards is rarely offered.
Of course everybody benefits from a lower price as well.
Indeed if there are 1-3 people joining me, I'm happy to order the boards!
Please let me know if you're interested, I want to order soon!
Mail me or post here, I will contact the guys who showed interest regarding payment in the next few days!
All the best, Hannes
From a quick look you can use the lm338 also; they have the same pinout. However you would need to bend the leads a bit, since it's a different package (TO-220 vs TO-3P of the LT1083). I will see if you can add some additional pads to the board, but don't get too excited, there's only little space.
Acutally I don't know exact price breaks as I didn't plan for a real large-scale group buy. I need some boards for myself and thought that maybe others would needs some as well, since that kind of regulator boards is rarely offered.
Of course everybody benefits from a lower price as well.
Indeed if there are 1-3 people joining me, I'm happy to order the boards!
Please let me know if you're interested, I want to order soon!
Mail me or post here, I will contact the guys who showed interest regarding payment in the next few days!
All the best, Hannes
To keep things flowing good, here is reading for you.
Set up a wiki page first and collect the interest, then get an offer from your pcb house, after that create a real list and start to get money from people. If you want some help with the setup, send me a message.
It's very easy to mess up things you see and it may be much money involved. Make sure you charge enough because you have costs for envelopes etc.
Set up a wiki page first and collect the interest, then get an offer from your pcb house, after that create a real list and start to get money from people. If you want some help with the setup, send me a message.
It's very easy to mess up things you see and it may be much money involved. Make sure you charge enough because you have costs for envelopes etc.
Thanks a lot for your generous help, P-A!
Indeed for a large group buy a wiki and good book keeping skills are a must
So just to summarize:
Costs
Currently 9 Euro per board, 14 boards total.
Expect for a small number of boards about 5 Euros shipping (worldwide) without personal receipt and 7 Euros with personal receipt; for 8+ boards add about 2 Euros for the increased weight.
Europeans get cheaper shipping, about 3 Euros without and 5 Euros with personal receipt.
I will wait for a few more days, say to the weekend and then I would like to start collecting the cash.
Payment options are Moneybookers, bank transfer or sending me plain cash (if you take the responsibility). Paypal still is not able here to offer their service to people without credit card, so I'm honestly sorry, I cannot offer this option.
I just read prototyping in P-As list: people, be aware that the board was not prototyped. I did my work to the best of my abilities and of course I do everything to ensure its proper functioning, but nevertheless it is not tested. Please only join if you are comfortable with this.
Have fun, Hannes
Indeed for a large group buy a wiki and good book keeping skills are a must
So just to summarize:
Costs
Currently 9 Euro per board, 14 boards total.
Expect for a small number of boards about 5 Euros shipping (worldwide) without personal receipt and 7 Euros with personal receipt; for 8+ boards add about 2 Euros for the increased weight.
Europeans get cheaper shipping, about 3 Euros without and 5 Euros with personal receipt.
I will wait for a few more days, say to the weekend and then I would like to start collecting the cash.
Payment options are Moneybookers, bank transfer or sending me plain cash (if you take the responsibility). Paypal still is not able here to offer their service to people without credit card, so I'm honestly sorry, I cannot offer this option.
I just read prototyping in P-As list: people, be aware that the board was not prototyped. I did my work to the best of my abilities and of course I do everything to ensure its proper functioning, but nevertheless it is not tested. Please only join if you are comfortable with this.
Have fun, Hannes
It's not a good idea with a non-tested pcb. 
We have had successful group buys but the boards have also been debugged properly. Why don't you order from Olimex a couple of boards first? People here are used to professional boards in most senses.
My advices:
We have had successful group buys but the boards have also been debugged properly. Why don't you order from Olimex a couple of boards first? People here are used to professional boards in most senses.My advices:
- Check the design!
- Write pcb name in every layer (but in some layers it can be placed outside the board)
- Write revision number or letter in every layer
- It's also a good rule to write the layer name in the layer
- Correct the silkscreen so all designators are clearly visible when the parts are mounted
- Check trace widths. Unnecessary thick traces in some places
- Check drill sizes. > 0.2 mm more than the thickest component pin
- Check pad sizes (a bit small in some places)
- Check part dimensions with the pcb symbols
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P-A, you really take care of us!
It's up to everybody to decide for himself. This is a simple regulator board with a handful of parts, so I'm confident about it.
(Honestly I have the impression that a lot of the group buys here are about untested boards, but it is never clearly mentioned.)
Anyway, please understand that I'm not a professional business. I do not offer a commercial product. I just offer the possibility to get some boards that I would have ordered anyway.
I highly respect your attitude and your efforts to provide highest quality boards, P-A. However if I have to order prototypes first, assemble and test them and offer boards then, it costs a lot of time and money (prototypes), so I would have to charge these additional costs, even if I don't charge my working time. And who wants to pay that?
You will be astonished, P-A when you will see my Cello pcb buy. Much more complexity! But I'm now working on it for a couple of months now and I'm again confident that it will work Will this be the road to perdition? We'll see 
Of course I will extensively check the boards prior to sending them to the board house, including checking all used part libraries, schematic, pinouts...
Well, you don't do simple boards, do you?
Thank you for all your tips, they will not be forgotten.
All the best, Hannes
Now that completely escapes me. What's the disadvantage? I can only imagine that they're harder to solder? An updated artwork did already consider this
It's up to everybody to decide for himself. This is a simple regulator board with a handful of parts, so I'm confident about it.
(Honestly I have the impression that a lot of the group buys here are about untested boards, but it is never clearly mentioned.)
Anyway, please understand that I'm not a professional business. I do not offer a commercial product. I just offer the possibility to get some boards that I would have ordered anyway.
I highly respect your attitude and your efforts to provide highest quality boards, P-A. However if I have to order prototypes first, assemble and test them and offer boards then, it costs a lot of time and money (prototypes), so I would have to charge these additional costs, even if I don't charge my working time. And who wants to pay that?
You will be astonished, P-A when you will see my Cello pcb buy. Much more complexity! But I'm now working on it for a couple of months now and I'm again confident that it will work
Will this be the road to perdition? We'll see Of course I will extensively check the boards prior to sending them to the board house, including checking all used part libraries, schematic, pinouts...
Well, you don't do simple boards, do you?
Thank you for all your tips, they will not be forgotten.
All the best, Hannes
Now that completely escapes me. What's the disadvantage? I can only imagine that they're harder to solder? An updated artwork did already consider this
Attachments
Quite the opposite, most boards are excellent when it comes to bugs. I think we have created here a sort of professional way of doing group buys but we have had also a couple really embarrassing ones too so I see it as my duty to eliminate bad offers and bad administration.h_a said:
When you mention money, prototyping costs will be charged from the buyers so the golden rule if you read my instructions is not to put money into it and also do a prototype run if you plan to make many boards. This is why you have a wiki with the interest. If yo have 100-200 or more boards, you don't order them without a prototype run. I wouldn't do it. Even a simple board can fail in to process. Personally I wouldn't offer boards with irritating bugs. My goal is "spitzenklasse" within the design goal.
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