µCurrent GOLD on Kickstarter

[neslekkim]

Unit 00834 arrived in Norway

[fuffkin]

Don't go for it - it's another bl**dy scam. It'll never work!!! 

Mine arrived many weeks ago, tested and working well. I see the battery LED is on all the time, presumably to stop you leaving it on like the old one (which I was always doing). Unfortunately, I still leave this one on too. What can you do??? Nice try though.....

[OldTech]

@EEVblog

Dave,

When do you expect the new µCurrent Gold to ship to Adafruit?

OldTech

[MLXXXp]

Don't turn it on. Take it apart!
Void the warranty.
Try to make it better.
Put it back together.

I received my Kickstarter uCurrent Gold, serial number 798, in Toronto, Canada on May 13. It was mailed on May 2.

I've spent some time making changes to it:

• Change on-short to off-short
• Lower the LED brightness
• Add some input protection when off
• Increase the positive measurement range
• Lower the case

Here are some details:

• I don't see a need for it to be powered on when the power switch is in the "SHORT" position. It will just read 0 anyway. I cut the trace between SW2 pins 1A and 3A.
  
  
• I found the "BATT OK" LED to be too bright for my liking, even when the battery voltage was near the low limit. I replaced the 270R resistor, R4, with a 470R one. With 470R, the LED current is between 1.3mA and 1.9mA and it's still plenty bright. Since the LED uses more power than everything else combined, I estimate that the battery will probably now last 30% to 50% longer or maybe even more.
  
  
• It's difficult to know what kind of protection the inputs of U1, a MAX4239, have. The datasheet only specifies the maximum input voltages. It doesn't say what happens, or how much current is safe, if these voltages are exceeded. I didn't want to affect the circuit when powered on, but I figured it couldn't hurt to add back-to-back 1N5820 3A Schottky diodes across the inputs when the power is off. To do this, I added a jumper between SW2 pins 2B and 3B and put the diodes from SW2 pin 4B to the big trace connected to the minus side of R1. Note that this does nothing to protect the input when the power is on. I've discussed this previously in this post:
  https://www.eevblog.com/forum/crowd-funded-projects/current-gold-on-kickstarter/msg376311/#msg376311
  
  
• I don't expect I'll often use the uCurrent to measure AC or other currents that swing both positive and negative. I felt it would be nice to have a larger range for single polarity measurements. I realised that this could be accomplished by shifting the virtual ground, by changing the values of R6 and/or R7. This would give a larger range for one polarity at the expense of lowering the range for the other polarity.
  
  Rather than just hard wire a new ground level, I decided to use a switch. I bought a small 1P3T slide switch with the intent to switch another resistor in parallel with either R6 or R7. The three switch positions would allow the virtual ground remain centred, be shifted higher, or shifted lower. However, after examining the datasheet for U2, a LMV321, I noticed that the virtual ground was already close to the high end of the input common mode voltage range. Shifting the virtual ground higher any significant amount, to extend the negative range, would not be possible. Even if U2 could do it, U1 and U4 have similar limitations.
  
  Since I already had the three position switch, I decided to add two more selections that increase the positive range. Position 1 leaves the circuit unaltered, with the original range of +/-1250mV. Position 2 switches a 30.1K resistor in parallel with R7, for a range of at least +2000mV and -400mV. Position 3 switches a 2.49K resistor in parallel with R7, which shifts ground almost to 0, for a range of +2400mV but only about -50mV. You can't bring the virtual ground all the way to 0 because even though the LMV321 is specified as having a rail to rail output, it can't really go all the way to 0 and neither can the U1 and U4.
  
  The switch I used is a NKK SS14MDP2. I drilled holes close to the edge of the board, between the output terminals. Unfortunately the switch covers up the word "VOLTAGE" of "VOLTAGE OUTPUT". I had to remove the circuit board copper around the holes to prevent shorting the pins. I also had to relocate the serial number sticker (did I void my warranty? ). The best place I found for this sticker ended up partially covering the graphic of Dave (Sorry Dave  ). I plan to put a label on the output side of the case, to indicate the range values.
  
  
• I don't intend to add larger batteries or anything else under the circuit board, so I cut the case down to a height of about 18mm. I could've gone even lower except for the way I mounted the protection diodes. (BTW, my uCurrent came with the black case screws.)

[EEVblog]

Well done on the mod, looks nice.

[EEVblog]

For all those who have asked, the µCurrent is now available from my new store:
https://eevblog.myshopify.com/

No plans to sell it through the distributors like I did last time.

[GeoffS]

S/N 1511 has arrived in sunny Tasmania.

Thanks Dave.

[Legit-Design]

For all those who have asked, the µCurrent is now available from my new store:
https://eevblog.myshopify.com/

Does this already include shipping? Quick browse through or search didn't reveal this secret. Most annoying thing when checking a store on web that doesn't clearly state what are the shipping costs. I assume it's already included in the price for international shipping? Or still Add $12 AUD to ship outside Australia?

No plans to sell it through the distributors like I did last time.

Did you forget:
http://clickingbad.nullism.com/ ?
Golden rule of moving product: Distribution, Distribution and Distribution
I think it was one amp hour show. You get less profits if someone else does it, but you are able to move more product and worry less. And you get the advantage of people getting to order more things at once from a store they want to order from.

Any chance you will get a HUGE batch of ucurrent golds in the future and sell them at a discounted price? So people who want one but don't have the extra will have no excuse to get it while it's cheap? Maybe when you hit 1000 episodes, or 200k subscribers? Doesn't have to be crazy cheap, just below the pain threshold.

[mtdoc]

 I ordered mine.
 It was quick and easy, 2 min,
 Free International shipping!.

Wow- so less expensive that the Kickstarter campaign.....

[MLXXXp]

I found the "BATT OK" LED to be too bright for my liking, even when the battery voltage was near the low limit. I replaced the 270R resistor, R4, with a 470R one. With 470R, the LED current is between 1.3mA and 1.9mA and it's still plenty bright.

I decided that the LED was still a bit too bright for me with the 470R R4, so I've now put in a 1K. This is fine for me, although a 1.2K or even 1.5K would probably still be bright enough.

With 1K, the LED current is 1mA with power at 3V. It drops to 0.72mA at 2.65V, which is the threshold where my unit's LED goes out.

I measured my unit's total current draw, with nothing connected, and found it to be 2.28mA at 3V and 1.95mA at 2.65V. Calculating the current for everything other than the LED, by subtracting the LED current, you get 1.28mA at 3V and 1.23mA at 2.65V.

For readings other than 0, additional current will be drawn by the gain resistors of U1 and U4. E.g. at 1V output the unit will draw an additional 0.11mA

[centon1]

Toronto,Ontario Canada
#00372
Sent: May 6th
Received: May 22nd

Nice PCB and impressive re-flow. Tightened one 'binding post' out of the package, other than that its beautiful.
Cursory testing has two thumbs up.

Thanks Dave.

[EEVblog]

Wow- so less expensive that the Kickstarter campaign.....

For aussies, no, the same price.
For international, yes, cheaper than Kickstarter.
Because when I ran the Kickstarter I expected to pay a high price for international shipping, but I have now spent the last several months setting up and refining an Australia Post commercial account that lets me get cheap international rates. It's actually now slightly cheaper for me to ship something international than it is to ship within oz.

[EEVblog]

Does this already include shipping? Quick browse through or search didn't reveal this secret.

Yes, free shipping anywhere in the world.
Extra if you want overseas tracking.

Did you forget:
http://clickingbad.nullism.com/ ?
Golden rule of moving product: Distribution, Distribution and Distribution

Not all rules apply to all situations.
I am in a position where I have a large audience, and a product niche enough that "passing trade" sales on distributors websites are small. So there is no benefit in having distributors from that point of view.
Also, I just spend many months and a lot effort setting up a commercial account and a system that lets me ship stuff efficiently and cheaply. To now not take advantage of that would be very silly.

You get less profits if someone else does it, but you are able to move more product and worry less.

You get a LOT less profit. In fact the distributors make more on the product than I would.
Also, the customer likely ends up paying more for the item, because
a) I can offer free shipping anywhere in the world and absorb the cost into my larger margin
b) I can't sell at a crazy low price to the distributor and make a reasonable return from it, so it's likely for the distributor to sell at a higher price than me in order to maintain the >40% markup they want.
Either way the customer loses.
The only way the customer gains by me using a distributor is that they can get the product quicker locally, and/or potentially bundle shipping with other stuff they want.

And you get the advantage of people getting to order more things at once from a store they want to order from.

That's not an advantage for me.

Any chance you will get a HUGE batch of ucurrent golds in the future and sell them at a discounted price?

Doubt it, because the price does not really come down with more volume. I've already hit the price deduction point.

[Legit-Design]

Is there general topic for new EEVblog store? Just noticed main eevblog.com page has link to store but it's the old store http://www.eevblog.com/shop/ while new store is at https://eevblog.myshopify.com/
Maybe also include µrulers with all different colours in your store? Or time for new crowdfunding campaign, this time Indiegogo, maybe even flexible funding?

[Kean]

this time Indiegogo, maybe even flexible funding?

LOL, that's really funny!!   

[Turtle9er]

Just received my uCurrent, however having a few issues, and also have a few questions. First, the issue I am having is that as soon as I put in a 2032 battery and turn it on, the battery drains in about 60s. I am using a BR2032, I know it is rated at less mAh than a CR2032, however I assume that is would still last longer than 60 seconds. I have since powered it by 3AAA so I could at least try to use it, but I am measuring 7mA of current draw when it is turned on. Does this seem normal (using 1.2V eneloop batteries for reference).
Now my questions are, can I just connect the output directly to an oscilloscope? I have seen a couple of references about connecting it and being careful about something, but not exactly sure what that means. The other question is, I actually need to measure a current range from +-10mA. This means on the 1mV/mA range, I at the very  bottom of the range, however I can't go up to the next range because I am then over the limit of +-1250uA. Would I be able to remove the 10R resistor (R9) and replace it with say a 1R or .1R and reduce the range on the 2nd setting? I was hoping to use this device to measure the current that is applied to subjects during neurophysiology experiments, because at the moment we are using hall effect sensors and they have not been that reliable etc.
Sorry if this is the wrong thread to post in, but does not seem there is a dedicated ucurrent thread addressing issues etc. Thanks in advance.

[MLXXXp]

First, the issue I am having is that as soon as I put in a 2032 battery and turn it on, the battery drains in about 60s. I am using a BR2032, I know it is rated at less mAh than a CR2032, however I assume that is would still last longer than 60 seconds.

The BR2032 also has a lower output voltage, of about 2.8V, than a CR2032 (about 3V). The relatively high current draw of the µCurrent is probably quickly pulling this down below the 2.65V threshold of the BATT OK LED. The battery probably isn't drained but it's unable to supply a high enough voltage. I'd try a fresh CR2032.

I have since powered it by 3AAA so I could at least try to use it, but I am measuring 7mA of current draw when it is turned on. Does this seem normal (using 1.2V eneloop batteries for reference).

A fully charged Eneloop AAA will be at about 1.3V with a 7mA current draw, so 3 in series will be 3.9V. Dave measured 7.2mA from the LED alone at 4.5V and I've measured the rest of the circuitry to draw at least 1mA, so your measurement of 7mA total at 3.9V sounds about right.

Now my questions are, can I just connect the output directly to an oscilloscope? I have seen a couple of references about connecting it and being careful about something, but not exactly sure what that means.

I'm guessing one of the references is one of my posts:
https://www.eevblog.com/forum/testgear/is-there-a-video-on-the-proper-usage-of-the-micro-current-gold/msg449116/#msg449116
I would watch Dave's video that xquercus refers to in a following post:
https://www.eevblog.com/forum/testgear/is-there-a-video-on-the-proper-usage-of-the-micro-current-gold/msg458742/#msg458742

Would I be able to remove the 10R resistor (R9) and replace it with say a 1R or .1R and reduce the range on the 2nd setting?

The 10K R2 is always in the circuit. To compensate for this, R9 is placed in series with R1 when on the µA range, which gives an overall resistance of very close to 10R. If you were to replace R9 with a 1R, you would get an overall shunt resistance of 1.0099R so have an error of about 1%. With a .1R you would get  0.101R. For proper readings R9 would have to be 0.9901R or 0.09R.

If you only need one range, I'd instead replace R2 (10K) with either the 1R or .1R that you propose and put the switch on the nA range. Note, though, that this would severely mess up readings on the other two ranges.

[Lupin]

I am working on making test applications on ATE / "Automated Test Environment" machines and we get a lot of projects involving automotive electronics.
On most of these projects the measurement of standby current consumption is essential and it's very important for our customers to ensure a correct standby current.

So I have pretty much taken the µCurrent design and changed it to fit my own needs.
I plan to change the shunt depending on the actual application / the current that I want to measure.
Amplification is x100 like the µCurrent and output voltage should be in the 1V range so that the 1V range of my voltmeter can be used.

• First of all the output voltage should be ground referenced, thus a charge pump for generating negative OP amp supply is needed.
• I also changed the OP-Amp to one that's easier to source for me and still offers quite good specs. I also don't need very high precision because we just need to ensure that the standby current consumption is "about right". It's more important to have reproducible measurements.
• I also don't need multiple ranges. For high currents (active current of the DUT / "Device Under Test") i can just read the power supply.
  I just need a circuit that helps to measure currents in the 1 to 100 uA range.
• I also added a "burden voltage limiter", basically a shunt regulator limiting the burden voltage to something of about 20mV regardless of the current.

I attached my circuit here and want to bring that last addition to your attention.
Most loads (e.g. a microcontroller circuit) have high dynamic range current consumption.
The load might stay in standby mode for most of the time, drawing only little current.
From time to time the load will wake up and do something that consumes a lot more current.

Now if the µCurrent is set to 1250nA range (10k shunt resistor) then the load won't be able to wake up properly because the 10k shunt resistor is limiting the current to the load. And even if the circuit can wake up, the increased current draw of the load will cause the load voltage to drop.

For that reason i added that "burden voltage limiter". As soon as the burden voltage increases to something above 20mV the MOSFET will turn on and ensure that the load voltage won't drop.
This way you also don't have to worry about setting the correct current range.

Though I am unsure of how much this will affect the actual measurement.
I guess the OP-Amp IC4 in my circuit will have some small input current and the OFF-state resistance / leakage current of Q1 will also cause some error.

What do you think, does this circuit make sense?
How big is the error introduced due to that circuit? Any ideas to reduce the error? Maybe I can make a better choice of components for this?
Can this be a possible addition to the next µCurrent? If the effect on the measurement is too big it can be made so, that it can be switched on / off.

[EEVblog]

The uCurrent is limited to those 3 fixed ranges, and that can be an issue in many cases.

[Lupin]

I wasn't exactly getting at the ranges. In my application I am fine with one range and unipolar measurement.

The main reason I added that voltage drop limiter is to be able to leave the load connected regardless of load current - without having a significant drop in load voltage.

[pizm83]

Should I get worried if I still did not get my uCurrent from the Kickstarter campaign?
Is anybody else still waiting for his unit?
I am starting to think it might got lost somewhe in transit

[EEVblog]

Should I get worried if I still did not get my uCurrent from the Kickstarter campaign?

Yes!
What is your name and kickstarter email address? (private if you prefer)

[pizm83]

Should I get worried if I still did not get my uCurrent from the Kickstarter campaign?

Yes!
What is your name and kickstarter email address? (private if you prefer)

I have already send You a PM about two days ago about this, I hope that the info in that PM is sufficient, if not then please PM me:-)

[pizm83]

Dave
please reply to my PMs
(sorry for spamming in the topic)

Should I get worried if I still did not get my uCurrent from the Kickstarter campaign?

Yes!
What is your name and kickstarter email address? (private if you prefer)

I have already send You a PM about two days ago about this, I hope that the info in that PM is sufficient, if not then please PM me:-)

[NDT]

Dave,
I've sent you several PMs because I've never received my uCurrent from the Kickstarter campaign. Please could you address this situation?