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Little Bee Current Probe

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Weston:
I have mentioned in some previous posts I am working on a (relatively) low cost DC capable current probe. Since then the project has been accepted by Crowd Supply and as of today it has a pre-launch page! https://www.crowdsupply.com/weston-braun/little-bee

I am still working on finalizing the final design for the crowd funded campaign, so I figured now would be a good time to post about it in case anyone has feedback.

The key specs are a bandwidth of DC-10MHz, a sensitivity of 0.25V/A and a maximum current of +/- 5A. It also can operate in a magnetic field mode, similar to the i-prober 520.

Feedback / commentary is welcome! I am hoping to launch the campaign in the next month or so. Right now I am in the process of finalizing the design and collecting price quotes for manufacturing. Final sales price should be between $100 and $200 USD.
 

PlainName:
Looks interesting!

I'm in two minds about the battery. Great that it is battery-powered but the 4-hour life is perhaps a bit short. That's going to mandate Ni-MH... presumably the lower 'full' voltage of these won't be a problem? Would having a built-in LiIon improve life? If so, the cost of a simple USB charge circuit may be worth it (to the user). I can appreciate that you might not want to run it when connected to a USB charger, but that situation isn't unusual enough to raise eyebrows.

Weston:
Thanks for the feedback.

The last revision draws  ~0.35W from the battery, so 4h of battery life is probably on the conservative side. The last revision consumes more power than the previous ones because I am supplying a higher sensor voltage to increase the SNR. The boost converter runs down to ~0.7V, so a Ni-MH battery will work fine.

Lithium Ion batteries are a nightmare for small scale shipping, so that is out.

I am working on the final revision now and looking at adding a footprint for a small JST connector so people can use the probe with an optional external power adaptor.

thm_w:
Nice to see.

Is that front loop part 3D printed or some kind of cast? How does it open?

Weston:
The front loop is a flux concentrator which allows for sensing the current in a wire with higher accuracy than field mode. It clips on the front tip. Its 3d printed plastic, same as the tip cover, and has a gapped ferrite torroid inside.

Before you clip it on, you can put it over a wire, so there is no need to thread the wire through / cut the wire to pass it through. The opening, which determines the maximum wire you can slide it over, is 4mm. I am still working on the geometry of the plastic parts, so it might change a bit, but it's going to be something close to 4mm for the final version.

Here is a close up:


 

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