281 clone project- taking orders now for last run of these..

numbertalk · Posted: Fri Aug 08, 2008 11:16 am Post subject:

Started collecting parts for a build and am having trouble finding an L7810 anywhere (Mouser said the part they used to carry is now obsolete) - could anyone tell me where I could get one in the states (or a correct substitute - I'm building 4 boards so don't think I could use the less beefy one that's been mentioned elsewhere in this thread).

Edit - found this one:

http://www.mouser.com/Search/ProductDetail.aspx?qs=4kLU8WoGk0vJnJbo9hrOCg%3d%3d

would this be enough for 4 boards? I guess since they're in pairs I should say for 2 boards.

Which is another question - the BOM says use 1 for multiple generators, but in the docs showing the difference between the A and B boards IC5 is on both boards - does an L7810 go on every board or one per pair?

Also, sorry if these are dumb questions, but didn't find anything in the thread or documentation to answer this but:

1) What are "LV+ and LV-", bead, low-ohm resistors? Could you recommend a value for these? Also, what is "bead" - I've seen this referenced in a few projects but haven't encountered it directly yet.

2) What is the difference within range you suggest for the trim pot (20-50K) - in other words, what are the reasons I'd pick a 20K over a 50K - how would this change the circuit?

3) What would you recommend as a high-quality .1-.18uf cap? I can't seem to find a polystyrene cap close to that range.

Thanks!

a.b.o.z. · Posted: Fri Aug 08, 2008 1:48 pm Post subject:

josh how do I wire peak in jack?
does it go to PI on B board?

thnx

ivan

toppobrillo · Posted: Fri Aug 08, 2008 4:13 pm Post subject:

numbertalk · Posted: Fri Aug 08, 2008 5:32 pm Post subject:

neandrewthal · Joined: May 11, 2007 Posts: 672 Location: Canada

Ok, I give up! I'll take 2 more Smile

/mr · Posted: Sat Aug 09, 2008 4:44 am Post subject: Quadrature

Hi, just a quick question:

The oscilloscope picture describing the Quadrature mode in your builder's guide
http://www.sdiy.org/toppobrillo/twoeightyone.html
seems to show some three-phase behaviour caused either by retrigging A at its end instead of at B's end, or by trigging A repeatedly from some external clock.

I suppose the b281 clones are capable of true quadrature as well? Smile

(where A is started at the end of B, giving four phases instead of the three in the picture)

PS. I haven't looked through the 21 pages in this thread for the answer, sorry.

ringer · Joined: Feb 20, 2007 Posts: 49 Location: montreal

Hi Topp,

I would like to order 8 boards. Please let me know when to transfer the funds, thanks.

Regards,
Ringer

a.b.o.z. · Posted: Sat Aug 09, 2008 8:56 am Post subject:

I've sent you PM Josh, I'm in for 2.

Cheers,

Ivan

toppobrillo · Posted: Sat Aug 09, 2008 4:52 pm Post subject:

numbertalk · Posted: Sat Aug 09, 2008 5:34 pm Post subject:

toppobrillo · Posted: Sat Aug 09, 2008 6:36 pm Post subject:

numbertalk · Posted: Sat Aug 09, 2008 7:01 pm Post subject:

Great - thanks again.

davemoog · Joined: Feb 23, 2008 Posts: 52 Location: Vancouver

Hope this helps someone.

I had built and tested all the boards individually and everything worked fine. I then proceeded to install the 4 boards into the panel and wired together. The cycle mode would stop functioning after a minute or so. The solution was to replace the ferite bead/jumper with 10 ohm resistors on all the boards. Problem solved!

This was with my bench supply and not my case supply - a "Power-One", which may have worked OK.

Also thanks to zthee who mentioned his power supply issues

toppobrillo · Posted: Sat Aug 16, 2008 9:06 pm Post subject:

dave- i would like to understand this better- are you saying that you had 4 FGs all cycling, or one? after about a minute's time it/they suddenly stopped? and how does this relate to zthee's problem? [hope you [zthee] figured it out by the way] anyways i am glad of course that it's not happening anymore, but i don't believe it should have required the changes that you made. i also really wouldn't suspect that your PSU is the problem, assuming that it's properly regulated and able to source enough current [not much]. so, if you wouldn't mind describing the circumstances/setup in more detail, i would appreciate it.

thanks!

Tronato · Posted: Sun Aug 17, 2008 1:43 am Post subject:

Hello!

I just PM'd ordering four!

Thanks!

TRON

toppobrillo · Posted: Wed Aug 20, 2008 4:19 am Post subject:

last day for orders.. if you haven't confirmed your order yet, you will be getting a PM from me shortly..

thanks!

hodad · Joined: Jul 31, 2007 Posts: 41 Location: atlanta

I'm in for four if I can still get in.

Thanks

Peake · Posted: Wed Aug 20, 2008 10:52 am Post subject:

Josh, I had ordered six from this new run- please cancel my order. I have "enough" of them already...thanks for the project!

Sine · Joined: Sep 10, 2007 Posts: 111 Location: Netherlands

No worry's ... I could use two extra Razz

..

topp ?

rjd2 · Joined: Sep 02, 2007 Posts: 236 Location: philly

are there a few resistors on the PCB that arent on the BOM? 13,18, 43 i think? i know there are 3 resistors that i couldnt find on BOM. anyone have these? also, there is a "c" cap that's in the top left corner, non polarized. 100nf ceramic? thanks for any leads.

toppobrillo · Posted: Thu Aug 21, 2008 1:28 am Post subject:

R13 is a 680 Ohm, R18 is 4.7K, and R43 is 220K- these last 2 were accidentally left off the BOM.

c is 100nF yes.

toppobrillo · Posted: Thu Aug 21, 2008 2:11 am Post subject:

updated the BOM [finally]

funkyfarm · Posted: Sat Aug 23, 2008 5:12 pm Post subject:

D11 OPTIONAL.

What is GATE Priority in cycle mode ?

Thank you.

lexvortex · Joined: May 14, 2008 Posts: 155 Location: Toronto

I'll take four if any extras come up Smile

Thanks,
Dave