Dynalo (Rev.C) construction thread

[Bizzel]

I'm trying to calculate the value of the power LED resistor, R67 and just wanted to check my working here.
 
The LEDs I'm using are these white models (889-LW500AM) from Mouser - vF of 3.3 and 20mA current draw. Source voltage is 15.4v. I used this calculator to derive the resistor value and rating and I get 680ohm, 0.5 watts. I notice the very first post in this thread suggests 4K for R67 so I find this result strange (if logical).

 

[nikongod]

20mA is the MAXIMUM rated current. 
 
A 4Kohm resistor gets you 
I=V/R
I=(15.4V-3.3V)/4000ohms=0.003A=3mA
 
I would try the LED at low current before you go testing the maximum rated current Many people find that low-power LED's at fairly low current are plenty bright for indicator lamps.

 

[00940]

Actually, for those leds, 100ma is the maximum current and 20ma the working current for the rated luminous intensity. see: http://www.optoga.se/pdf/LW500AM.pdf
 
Honnestly, you picked weird leds. As indicators, led rated for 3-5ma working current are bright enough. You might try them at 5ma and see if it's bright enough.

 

[nikongod]

My bad.

 

[Avro_Arrow]

Can some one (any one...) look over my Dynalo Schematic to see
if I made any errors? I've checked it over but another set of eyes
is always helpful.
 
Thanks!
 

 

[Avro_Arrow]

I already found one...it should be Kevin Gilmore, not David Gilmor...

 

[00940]

No errors, more like questions:
 
- why such a big cap (33uf) for the servo integration ?
- why diodes in serie with r19 ?
- why do you feel the need for a compensation cap with a gain of 10 ?

 

[Avro_Arrow]

1: It's hard to see in the drawing but it's .33, not 33. I guess I should write it 0.33uF.
2: It's in the Dynalo Rev. C schematic.
3: It's in the Dynalo Rev. C schematic.
 
Quote:

No errors, more like questions:
 
- why such a big cap (33uf) for the servo integration ?
- why diodes in serie with r19 ?
- why do you feel the need for a compensation cap with a gain of 10 ?

 

[Avro_Arrow]

Here, the caps are better labeled.
 

 

[bada bing]

A couple observations.
 
I've seen a touch of ringing on 100kHz square waves without some compensation.
About 5-10 pF for gain 11 increasing to 33pF at gain 2 quelled it nicely on a couple I've seen on a scope.
The dynalo mint tin boards from the group buy 5 years ago seemed to ring a bit more than the full size Rev C boards.
The rev C boards almost go overboard on film and 'lytic  rail caps everywhere, the mint tin boards had no rail caps at all.
 
I've built rev C with and without the thermal tracking diodes, I saw no harm but no benefit to including them.
 
00940 : You were involved with the mint tin board group buy from years ago ? Do you still have the board files ?
            I know the board files were posted and open source, but they are hard to find now.
       

 

[Avro_Arrow]

Has anyone built this with the j74/k170 or just
the j109/k389?
 
I was planning on using about 3 inches by 4 inches to draw my board.
I guess that would make it a full sized build. Each channel will have
it's own board.

 

[00940]

Quote:

00940 : You were involved with the mint tin board group buy from years ago ? Do you still have the board files ?
            I know the board files were posted and open source, but they are hard to find now.
     

Sorry, I just searched my drive and couldn't find anything  :-/  I was quite a noob at that times though and was more involved with setting up a small forum for building support and parts finding. Subsonic did the work for the pcb.
 
However, if my memory is good, the PCB was heavily inspired by that layout by Sijosae:
 

 
Just stick two, one next to the other. Details here: http://www.headphoneamp.co.kr/bbs/zboard.php?id=diy_sijosae&page=2&sn1=&divpage=1&sn=off&ss=on&sc=on&keyword=gilmore&select_arrange=headnum&desc=asc&no=17

 

[Pars]

 
Quote:

Can some one (any one...) look over my Dynalo Schematic to see
if I made any errors? I've checked it over but another set of eyes
is always helpful.
 
Thanks!
 

 
You seem to have the + rail and the feedback loop connected together/confused:
 


 

 

[Avro_Arrow]

Yes PArs, your right...I did that when I connected the Servo...ooopppssss 

I'm sure I would have caught that myself the next time I looked at it...thanks!

 

[nattonrice]

Hehe it would have made for an interesting sound.