Author Topic: µCurrent GOLD on Kickstarter  (Read 166283 times)

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Offline zbomz

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Re: µCurrent GOLD on Kickstarter
« Reply #300 on: January 23, 2014, 04:31:55 pm »
Hi All,

What a cool product! Unfortunately, I missed the Kickstarter campaign. I really want the uCurrent Gold, so I was really excited when I found the entire Altium project on EEVblog. I am planning on spinning a few of my own boards and hand populating them. I love open hardware! Thanks for sharing Mr. Jones. Has anyone found a BOM or parts list for the uCurrent Gold? Is there any way that it could be made available? I am not able gather all of the manufacturer part numbers from the schematic, and I want to be sure to get the right parts.

Thanks in advance!
 

Offline con-f-use

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Re: µCurrent GOLD on Kickstarter
« Reply #301 on: January 23, 2014, 07:35:48 pm »
I am not able gather all of the manufacturer part numbers from the schematic, and I want to be sure to get the right parts.

Good luck with that. Dave bought out the entire world supply on various of these components (see the latest video). You'll have to wait or find replacements. As to a parts-list: Earlier in the thread, Dave said he didn't have time to update the uCurrent's files.
 

Offline grimmjaw

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Re: µCurrent GOLD on Kickstarter
« Reply #302 on: January 24, 2014, 07:05:59 am »
Does anyone knows where Dave  have the board manufactured? and assemble?  :-//  From the latest video i assume different board manufacturer and assembler
 

Offline EEVblog

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Re: µCurrent GOLD on Kickstarter
« Reply #303 on: January 24, 2014, 09:15:32 am »
BOM has been added.
 

Offline Smokey

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Re: µCurrent GOLD on Kickstarter
« Reply #304 on: January 24, 2014, 09:32:31 am »
Based off the BOM from the last video and current distributor prices, 2000 assemblies looks like around 40,000 USD total parts cost.  Nice.
How much is your assembly house charging you per board to stuff them?  Are they going to do selective solder for the through hole parts?
 

Offline MLXXXp

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Re: µCurrent GOLD on Kickstarter
« Reply #305 on: January 25, 2014, 12:49:24 pm »
BOM has been added.
Note that the description for the LED in the BOM says it's orange but both Digi-Key and the datasheet for the part say it's yellow.
Also, why is the Supplier 1 Part # for the LED in the BOM in blue and underlined?
 

Offline hiddensoul

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Re: µCurrent GOLD on Kickstarter
« Reply #306 on: January 25, 2014, 10:15:46 pm »
BOM has been added.
Note that the description for the LED in the BOM says it's orange but both Digi-Key and the datasheet for the part say it's yellow.
Also, why is the Supplier 1 Part # for the LED in the BOM in blue and underlined?

Can you not just pick any colour LED if you are going to make this yourself ? Bearing in mind that the high intensity LED's will draw more current from the battery
Mark "Pockets" Clohesy
I hack with the battery in..
http://hamshack.org
VK3PKT
 

Offline con-f-use

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Re: µCurrent GOLD on Kickstarter
« Reply #307 on: January 25, 2014, 10:37:30 pm »
[...] the BOM says it's orange but both Digi-Key and the datasheet for the part say it's yellow.

I can't tell if my sweater is dark black or a slightly darker black. Can you help me?
 

Offline MLXXXp

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Re: µCurrent GOLD on Kickstarter
« Reply #308 on: January 25, 2014, 11:13:30 pm »
Can you not just pick any colour LED if you are going to make this yourself ? Bearing in mind that the high intensity LED's will draw more current from the battery
Sorry, I was just pointing out an error that Dave may have missed in the BOM. (The currently posted schematic shows it as green). I guess I came off as being a bit nit-picky.  :-[

The intensity of the LED doesn't affect the current draw. It's a function of the LED's forward voltage, the battery voltage, the voltage drop of the ouput driver, and the value of the resistor. Actually, a high intensity LED would require less current, for the same brightness, than a less efficient one.
« Last Edit: January 25, 2014, 11:16:49 pm by MLXXXp »
 

Offline hiddensoul

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Re: µCurrent GOLD on Kickstarter
« Reply #309 on: January 26, 2014, 07:22:41 am »
Can you not just pick any colour LED if you are going to make this yourself ? Bearing in mind that the high intensity LED's will draw more current from the battery
Sorry, I was just pointing out an error that Dave may have missed in the BOM. (The currently posted schematic shows it as green). I guess I came off as being a bit nit-picky.  :-[

The intensity of the LED doesn't affect the current draw. It's a function of the LED's forward voltage, the battery voltage, the voltage drop of the ouput driver, and the value of the resistor. Actually, a high intensity LED would require less current, for the same brightness, than a less efficient one.

yes I agree, I was referring to the optimum rating so a 20mA Red led would use less then a 50mA High intensity if driven at  full brightness, if you were derating the high intensity then yes it would use less power
Mark "Pockets" Clohesy
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http://hamshack.org
VK3PKT
 

Offline MLXXXp

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Re: µCurrent GOLD on Kickstarter
« Reply #310 on: January 26, 2014, 05:51:19 pm »
Regardless of inherent protection due to increased shunt resistance when switching ranges, and other factors, I'd still like to know what the maximum continuously sustainable safe current would be for each range [...]
Since nobody has replied about this and the BOM is now available, so we can get information for all the components, I'll take a stab at this myself. This will be a very conservative estimate based on the information available in the datasheets.

I'll assume that the worst-case scenario is with the power off. The shunts will still be connected across the current input terminals J1 and J2, and feed into the inputs of U1. None of the datasheets for the active components give internal schematics, so I'll assume that:
  • +V and -V will be held to the same voltage level through a reasonably low impedance (at least via the 200K of R6 and R7).
  • The inputs of U1 will have a very high impedance even with no power on the chip, at least within our safe operating range.
  • There will be a reasonably low impedance path between VGND and either +V or -V. Therefore, the - input of U1 will couple through R5 to VGND (and thus +V and -V), so will not be a factor. I can't be sure of this without internal schematics but it's the safest assumption.
Current through the shunts will impress a voltage upon the + input of U1 via SW1. The + input is high impedance, so the voltage on it will be equal to the voltage across the shunt resistor(s) selected by SW1. The only absolute maximum rating given for U1's + input is "(-V - 0.3V) to (+V + 0.3V)". I'll assume this is even with no power on the chip. No information is given on what amount of current or power is safe if we exceed these voltages, so we can't exceed 0.3V across the shunt resistors(s), with current flowing in either direction. To be safe we should probably lower this to 0.28V.

The other limits we have are the power ratings of the shunts and the current ratings of SW1's contacts.

For the mA range:
The shunt is 0.01ohm R1. SW1's contacts are rated 4A at 28V DC and no other higher currents are specified for other voltages, so we have to make 4A our maximum. R1 is rated 1W at ambient temperatures up to 70C. At 4A, R1 will draw 0.16W, so it's safe. At 4A, R1 will be at 0.04V, so U1 is safe.

For the uA range:
The shunt is formed by a series-parallel arrangement of R9, R1 and R2 but R1 and R2 are insignificant for these calculations, so we can just consider 10ohm R9 to be alone. The safe voltage of 0.28V across R9 will require 0.028A. R9 is rated 0.1W at ambient temperatures up to 70C. At 0.28V, R9 will draw 0.00784W, so it's safe. SW1 obviously is safe.

For the nA range:
The shunt for this range is 10Kohm R2. The safe voltage of 0.28V across R2 will require 0.000028A. R2 is rated 0.063W at ambient temperatures up to 85C. At 0.28V, R2 will draw 0.00000784W, so it's really safe (as SW1 still is).

Summary:

For the mA range, the maximum safe continuous current is 4A, which is 3.2 times the 1250mA full scale value.

For the uA range, the maximum safe continuous current is 28mA, which is 22.4 times the 1250uA full scale value.

For the uA range, the maximum safe continuous current is 28uA, which is 22.4 times the 1250pA full scale value.
 

Offline MLXXXp

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Re: µCurrent GOLD on Kickstarter
« Reply #311 on: January 27, 2014, 03:10:01 pm »
Since nobody has replied about this and the BOM is now available, so we can get information for all the components, I'll take a stab at this myself.
Thinking about my previous post a little further...
You could add some protection for U1's inputs when the power is off, without affecting the powered on circuit in any way. With power on, and providing that the battery good indicator is lit, the maximum allowed voltage on the inputs would be about 1.6V instead of 0.28V. I'd make it 1.5V just to be safe.

The mA range would still be limited by the switch contacts, so would remain at maximum 4A.

The uA range would now be limited by the power that the shunt can safely handle. R9 is rated 0.1W but to be safe I'd derate this to at most 75% (0.075W). At 0.085A R9 would draw about 0.072W and the voltage would be 0.85V, which is safe for the input.
So the maximum safe current on the uA range would now be 85mA instead of 28mA.

The nA range would still be limited by the input voltage. For 1.5V this would be 0.00015A at a very safe 0.000225W.
So the maximum safe current on the nA range would now be 150uA instead of 28uA.

Protection could simply be accomplished by switching a short across the current inputs when the power is off. However, in some cases it might be desirable for the shunt resistance to remain the same for both on and off conditions. This could be accomplished (for currents in a readable range, at least) by putting two schottky diodes back to back across the inputs. These would not conduct significantly at the 12.5mV required for full scale but would clamp at about 0.3V to protect the op amp input.

To modify the uCurrent, all that's required is to jumper pins 2B and 3B of SW2 and put the diodes (or a short) across pins 1B and 4B of SW2. If you wanted the diodes to benefit from whatever protection is offered by the PCB trace fuse, you would wire the diodes between SW2 pin 4B and the big PCB trace between the trace fuse and R1 (after scraping off some solder mask).
« Last Edit: January 27, 2014, 03:38:42 pm by MLXXXp »
 

Offline DaveW

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Re: µCurrent GOLD on Kickstarter
« Reply #312 on: January 28, 2014, 09:00:09 pm »
It looks like the shipping is working better than the uRulers; it arrived this morning in the UK,

Cheers Dave! Even included fudge...
 

Offline Christopher

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Re: µCurrent GOLD on Kickstarter
« Reply #313 on: January 30, 2014, 06:43:20 pm »
When can I buy one from a distributor/directly?  We want one at work...
 

Offline bronson

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Re: µCurrent GOLD on Kickstarter
« Reply #314 on: January 31, 2014, 08:22:31 pm »
Christopher, right now the best option might be to take Dave's schematic and make one of your own.  In a few weeks I bet we'll hear of some overrun for sale but that's pure speculation.  Here's hoping Dave's assembly house pulls a few ghost shifts...

 #22 arrived in Santa Cruz today.  Cheers Dave!  Happy to see the battery installed and ready to go but first ima eat this fudge.

Alas, the battery powered scale project that I ordered it for was canceled this week.  Now I need to find something else to use it on...
 

Offline nerdms

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Re: µCurrent GOLD on Kickstarter
« Reply #315 on: January 31, 2014, 09:14:02 pm »
#18 has arrived!  Unfortunately the fudge did not survive the unpacking to make it into the picture  ;D

Dave, one problem with the uCurrent is that we can't take it apart!

Beauty  :-+  :-+
 

Offline EEVblog

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Re: µCurrent GOLD on Kickstarter
« Reply #316 on: January 31, 2014, 09:17:31 pm »
Christopher, right now the best option might be to take Dave's schematic and make one of your own.  In a few weeks I bet we'll hear of some overrun for sale but that's pure speculation.

There will be no overrun until the 1200th unit or so, and I still don't have that many parts yet.
I have to ship all the KS units first.
 

Offline Tooms

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Re: µCurrent GOLD on Kickstarter
« Reply #317 on: February 02, 2014, 09:19:28 pm »


Hi


Got my ucurrent gold today here in Denmark.

Here is a blog post about it.
http://www.tooms.dk/Tblog/Showblog1.asp?BlogID=201402022205331797


Thanks Dave


Tooms
 

Offline idpromnut

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Re: µCurrent GOLD on Kickstarter
« Reply #318 on: February 02, 2014, 09:33:49 pm »
*Really* hoping mine will be waiting for me in the mailbox tomorrow after work!   :-+
 

Offline zax

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Re: µCurrent GOLD on Kickstarter
« Reply #319 on: February 03, 2014, 09:09:41 pm »
Hi!
 #25 has arrived.
Thanks Dave  :)
 

Offline Slothie

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Re: µCurrent GOLD on Kickstarter
« Reply #320 on: February 05, 2014, 05:48:05 pm »
#24 arrived in Blighty on 3/2/2014 - Just picked it up today. Came with the expected uRulers and some other bits - Fudge (Yum Yum!), a lithium battery a;ready installed (naughty Dave!), some banana plugs and.... 3 AAA batteries & battery box!

Not sure what the batteries where for - unless it was to throw Australia Post off the scent if they X-ray a package. They see dry cells and assume that noone would put lithium batteries in as well?

Anyhoo nice to get it at last. I'll be the one measuring things for the next couple of days... How many uA  does that calculator draw?  :)
 

Offline SeanB

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Re: µCurrent GOLD on Kickstarter
« Reply #321 on: February 05, 2014, 06:09:47 pm »
#24 arrived in Blighty on 3/2/2014 - Just picked it up today. Came with the expected uRulers and some other bits - Fudge (Yum Yum!), a lithium battery a;ready installed (naughty Dave!), some banana plugs and.... 3 AAA batteries & battery box!

Not sure what the batteries where for - unless it was to throw Australia Post off the scent if they X-ray a package. They see dry cells and assume that noone would put lithium batteries in as well?

Anyhoo nice to get it at last. I'll be the one measuring things for the next couple of days... How many uA  does that calculator draw?  :)

Don't you know Dave bough shares in Aus post office. Now he has to add weight to get them to give a dividend instead of making the usual loss. ;)
 

Offline bronson

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Re: µCurrent GOLD on Kickstarter
« Reply #322 on: February 07, 2014, 06:43:27 am »
and.... 3 AAA batteries & battery box!

I figured they came with the project box, as did the lid you won't use.

If not then I have no idea!
 

Offline idpromnut

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Re: µCurrent GOLD on Kickstarter
« Reply #323 on: February 10, 2014, 11:04:50 pm »
Unit #27 reporting in for duty from the Great White North!  Thanks Dave!  *goes to find stuff to measure*
 

Offline rjk5378

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Re: µCurrent GOLD on Kickstarter
« Reply #324 on: February 10, 2014, 11:36:28 pm »
Just a sanity check. I am assuming the "polling" on KS for the shipping addresses for the main batch (i.e., after the initial 200 units or so) has *not* happended yet. Is that right? I have not seen anything yet. I have been charged for my unit, and I am content to wait patiently, but just want to make sure I didn't miss it.  Thanks.

- Bob, KY3R
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