Doodlebug - USB Isolator
Feb 13, 2014 at 6:26 PM Post #76 of 305

fishski13

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no worries.  this is prototyping and a gift to the DIY community.
 
i just need the USB jack.  i ordered everything from Digikey this afternoon.
 
Feb 13, 2014 at 7:57 PM Post #77 of 305

tomb

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  no worries.  this is prototyping and a gift to the DIY community.
 
i just need the USB jack.  i ordered everything from Digikey this afternoon.


Thanks.  The correct jacks were ordered before I made that last post.  Hopefully, they'll all arrive on the same day.  I knew the Molex said "reversed," but just didn't realize that translated to the pinouts, too.  The one specified is about $4-$5, depending on where you are when you order it.  I just knew there were some cheaper.  Sure enough, Avro_Arrow found some.  I'll update the BOM for several versions - but not until I confirm that they all work!
 
BTW, the voltage/linear regulator part of the circuit works like a dream, at least with the spec'd 6VAC walwart from DigiKey.  I started out at 5.03VDC on mine and was able to very precisely adjust to 5.25VDC.  The trimmer works at about 0.02V per turn, giving you almost 1/2 volt of very precise adjustment.
 
Also, I can speak from experience, now - the prototype PCB's are very robust and can withstand a lot of re-work.  I removed the Type A USB connector and was able to save both the connector and PCB without damage - no lifted pads or traces.  
wink.gif
  
 
Feb 14, 2014 at 9:23 AM Post #79 of 305

muskyhuntr

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Hi All,
 
Got the power supply portion of the Doodlebug done.  No need for trouble shooting, came up first time!  Dialed in 5.000VDC and left it run for a half hour.  Stable.  Like Tomb, I was impressed with the precision of adjustment VR1 gives.  Only real problem I had was bending the diodes to the proper length (my problem not the boards).  SMD's were of the size that were easy to solder and placement of all parts was a piece of cake.
 
I do have a few suggestions though.
1) Make the pads for VR1 a bit larger.
2) Make the pads for the LEDs a bit larger.
3) ID polarity of LEDs on the board.
4) Put 6VAC and 9VDC by voltage in connector.
5) Would love to see a 5VDC output jack.  This device has uses beyond audio. For example robotics, micro controllers, protection circuit between computer and peripherals, etc.
6) Possibly in final product, have a provision to mount one of the LEDs to the front panel as an ON indicator.
 
Jim
 
Feb 14, 2014 at 10:05 PM Post #80 of 305

Avro_Arrow

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Time to take a break from house building and do some electronics...
 
Improvised work area (the rest of my "shop" is all in boxes).
 

 
For the SMD components, I used solder paste.
For the through hole components regular solder was used.
 
And...
 
It Lives!
 


Tested with the pupDAC and it works perfectly.
 
I'll give it a more detailed test tomorrow. I'm powering it with a 9 volt @ 500mA
adapter and the voltage at C5 is 13.5 volts with no load. I'll see what it is under
load. I might want to change C5 to a 25 volt part to be safe.
 
Before first power up, adjust VR1 all the way counter-clockwise.
 
Feb 14, 2014 at 10:17 PM Post #81 of 305

tomb

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  Time to take a break from house building and do some electronics...
 
Improvised work area (the rest of my "shop" is all in boxes).
 

 
For the SMD components, I used solder paste.
For the through hole components regular solder was used.
 
And...
 
It Lives!
 


Tested with the pupDAC and it works perfectly.
 
I'll give it a more detailed test tomorrow. I'm powering it with a 9 volt @ 500mA
adapter and the voltage at C5 is 13.5 volts with no load. I'll see what it is under
load. I might want to change C5 to a 25 volt part to be safe.
 
Before first power up, adjust VR1 all the way counter-clockwise.


Sounds great!
 
Yes, I'm familiar with working out of boxes right now.  I don't know what I've packed and what I haven't. Beezar is moving soon.
wink.gif

 
Anyway, great work on the prototype!!
 
Feb 14, 2014 at 11:44 PM Post #82 of 305

Avro_Arrow

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Anyway, great work on the prototype!!


Thanks Tom.
 
I had a chance to leave it running for a while and it barely got warm.
No problem using the 9 volt adapter.
Under load, the voltage at C5 dropped to less than 12 volts, so
I guess the 16 volt cap will be fine with this adapter as well.
 
I'm guessing most of the rest of you have the 6 volt @ 1 Amp adapter.
When someone gets theirs up and running, can you let me know the
no load and loaded voltage at C5?
 
Thank you to all the prototypers for your patients with us.
 
Feb 15, 2014 at 1:11 AM Post #83 of 305

fishski13

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i will measure across C5, but i don't forsee an issue as long as V=<16V.  caps should be able tolerate full rated V.  rated unloaded is 7.6VAC max plus a cap and minus diode losses.  you may get a goosed V on power up, but nothing i would worry about if transient.  the Panny FM are workhorses and spec great.  
 
Feb 15, 2014 at 3:51 AM Post #84 of 305

DingoSmuggler

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  i will measure across C5, but i don't forsee an issue as long as V=<16V.  caps should be able tolerate full rated V.  rated unloaded is 7.6VAC max plus a cap and minus diode losses.  you may get a goosed V on power up, but nothing i would worry about if transient.  the Panny FM are workhorses and spec great.  

With the 6VAC you'd just need to make sure minimum voltage under load is high enough so your dropping enough volts through the linear reg. On paper there should be plenty of headroom though measuring is certainly better.
 
 
Come production time... I've just remembered I've got a NOS SEGA 10Vdc linear plugpack, that should be well suited to this - maybe even crack it open to get an AC output. It never had a chance to power a mega drive, but it might get a chance to power a doodlebug.
 
Feb 15, 2014 at 7:57 AM Post #85 of 305

Avro_Arrow

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  With the 6VAC you'd just need to make sure minimum voltage under load is high enough so your dropping enough volts through the linear reg. On paper there should be plenty of headroom though measuring is certainly better.
 
 
Come production time... I've just remembered I've got a NOS SEGA 10Vdc linear plugpack, that should be well suited to this - maybe even crack it open to get an AC output. It never had a chance to power a mega drive, but it might get a chance to power a doodlebug.


Yes, the taget minimum voltage at C5 is 7 volts DC.
That gives enough headroom for the regulator to do it's job.
 
Feb 15, 2014 at 12:40 PM Post #86 of 305

fishski13

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i missed that point entirely.  hopefully the unloaded wart is putting out at least 6.4VAC or so then.  6.4*1.4142 = 9.1, or 7ish minus 2V diode drop.  i should receive the wart and other components in the the mail today.
 
Feb 15, 2014 at 1:40 PM Post #87 of 305

Avro_Arrow

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I think, in reality, the diodes only drop about 1.2 to 1.4 volts when

more lightly loaded like they are here. Even if the adapter drops
to 6 VAC when loaded, it should still be able to hit the minimum
7 VDC at C5. All assuming a maximum 500mA current draw.
 
6 * 1.4142 = 8.4852 so you can loose 1.5 volts and still be OK.
Also, the 317 really only needs about 1.5 volts to do its job.
2 volts just is a safer margin...
 
Feb 16, 2014 at 9:41 AM Post #88 of 305

tomb

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UPS says they're delivering both the connectors and resistors/caps/ferrites tomorrow.  So, I should be able to get them in the mail to you all on Tuesday.  Sometimes UPS changes their minds, though, and sends me an update saying it'll be a day later.  I'll keep you posted.
 
Feb 16, 2014 at 9:52 AM Post #89 of 305

fishski13

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stuffed the PS circuit.
 
getting 7.7VAC from the T1124-P5-ND wall wart.  voltage at C5 is 8.9VDC.  at 200mA and 3.65 voltage drop at 5.25V output, that's 0.73W or so dissipation.  
 

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