I will need to validate the component values on the board but 12V should not be an issue as the Boron can take 12V on VUSB.
Thanks for the suggestion.
Chip
I’ve been using the NCD Electron carrier that supports input VDC of 5-32V. For marine and auto 12V DC systems, charging voltages can exceed 14V. Cheers
You can always put a voltage regulator in-line to step the voltage down from 32 to 12V. However, if you want to power this circuit with 12V and need protection from over-voltage, I believe I could simply add a single Zener diode to prevent the voltage from going over 12V.
The only question would be choosing the right breakdown voltage for the Zener.
Here is one that costs about $0.12 and would be easy to add after the input fuse. Anyone with more experience in this is welcome to make suggestions. The more I think about this the more I think adding this protection is a good idea to prevent over-voltage from damaging the circuit. Thanks for mentioning.
Chip
You are better off getting something like this to cope with the severe electrical environment in automotive applications https://www.pololu.com/product/2831
I don’t have any experience with automotive so thank you for chiming in.
As for the input voltage range, the BQ24195 seems to be able to handle up to 17V so, adding a Zener with a 13-14V clamping voltage would seem like a cheap insurance policy. I understand there may be other factors like noise and transients that an external module like you proposed still makes sense.
Still, adding a Zener with a
@chipmc - if your initial use case did not include automotive, I suggest you try not to solve this problem. There are lots of things to pay attention to when designing automotive electronics, and a simple zener (especially not a $0.12 part) and a fuse will not save you in any meaningful way.
You risk getting pulled into feature creep by others wanting to take your design outside the parameters you set for yourself at the start.
Finding the balance between helpful enhancements and feature creep is often problematic.
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Andy,
Agree. My use case is outdoors and the fuse and varistor. I guess I was wondering if over voltage protection would be a good idea even for my use case.
Much as I love to see new uses for my boards, will need to leave automotive to someone who has understanding of that space.
Thanks, Chip
Do you know the manufacturer and part number for the I2C connector that NCD uses?
RS-Components #797-8792 ( Molex SL 70555, 2.54mm Pitch, 4 Way, 1 Row, Right Angle PCB Header, Through Hole)
Thanks - I looked around their website but didn’t find this info.
https://za.rs-online.com/web/p/pcb-headers/6792525/ try this, or just search this “Molex SL 70553, 2.54mm Pitch, 4 Way” in google
I dont Think this is a especially good circuit. If the input voltage goes above the breakdown voltage of the zener, the zener will effectively short circuit and you will blow the fuse.
In order to create a voltage regulator you would need a resistor in series with the fuse and in order to calculate the value of that you would need to know both the input voltage as well as the maximum current (Iz) of your load.
Better to use a step down converter or some other type of voltage regulater such as a LM7812 or similar
Oops, you are right. That is what I get for thinking there was an “easy button”. I will stick with the circuit I have now which has been tested and is reliable.
Thank you, Chip
OK, getting close to final here. Plan on getting a few boards and seeing what I need to fixe before sending off to MacroFab.
Added two Grove connectors - one for i2c and one for A0 and A1. Ran out of room to add more at least unless I wanted to switch over entirely. Will play with this one first.
Updated IO schematic
Top View of Board
Unless anyone sees something amiss, going to call this Rev one and get one made for testing.
Thank you all for you comments and suggestions.
Chip
2 Likes
Hey @chipmc, I’m wondering about the via fields you have around the ground pins of C8 and J4/5.
I doubt there is a lot of current, but if you are expecting a lot of current you also need a better connection on the + pins. The old pictures show a skinny trace.
Good point. Widened the power path to 32 mils which should be enough to carry up to 1A with 1oz copper.
Looks like this now.
Sending to the fab tomorrow morning.
Any more comments or suggestions?
Thanks,
Chip
1 Like
Have you checked the clearance for washers, nuts and bolt heads around your mounting holes, especially when components are mounted.
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Am using nylon screws but, gave them a little more room. Thank you for the suggestion.
All,
Sending off to the board house today. I will post again once I have made a few and tested them. Thank you all for your suggestions.
Again, this Repo has all the latest files incase you want to take this design make your own changes.
Chip
4 Likes
hi Chip,
i got some electron carrier boards you placed on osh park shared projects a little over a year ago for a project i was part of and wanted to ask if these 3rd gen carrier boards [unpopulated] will be offered. it looks like you are not doing osh park on this project. i realize all the files are up on github but wanted to check costs of bare boards you may have vs. doing a new setup order somewhere. thanks.
I hope you are having good success with the Electron boards and thanks for your interest in this board.
I am using OSHPark for the boards and do plan to share the project like last time. Based on some earlier feedback, I generally want to get a few made and test them for functionality before sharing the project. I should have these boards back within a week or so and will share the project then.
I also plan to do some production runs at MacroFab and will give folks a chance to get in on that so we might lower the per unit cost with a higher volume.
Hope this helps,
Chip
1 Like