[Ovmsdev] OVMS CAN-USB Call for Assistance

Mark Webb-Johnson mark at webb-johnson.net
Wed Sep 4 07:56:31 HKT 2013

Last time I checked, we were paying about 65cents for the MCP2551 ICs, so they are not too bad. They certainly simplify things and are a proven technology.

Regards, Mark.

On 4 Sep, 2013, at 7:50 AM, HONDA S-2000 <s2000 at sounds.wa.com> wrote:

>> On Sep 2, 2013, at 22:08, Mark Webb-Johnson wrote:
>>>> I'll try to rough up a schematic, to see how many components this can be brought down to. For China manufacturers, saving even 1 component brings the cost of both materials and assembly down. I remember working with the factory to remove 1 single chip costing US$1.10 down to a bunch of passive components costing US$0.10 - resulting price difference was US$3 (I think they really didn't want to use that chip, not just for the cost but also for the hassle of obtaining it).
>>> So, passives do not count as a whole component, not compared to a chip?
>> Supposedly not. Or, at least they don't concern themselves with them. I suspect that the factories have rolls of hundreds of thousands of these components, ready to go. Sometimes if I specify a 2.3k resistor, for example, they will come back and ask to substitute with 2.2k - but that happens surprisingly rarely. Their biggest concern seems to be the ICs - or maybe they are just concentrating on things that cost more than a buck.
> I find myself wondering whether the MCP2551 could be replaced with 2 or 4 transistors and a handful of passives. Unfortunately, it would add significantly to the research effort to design a discrete circuit. The block diagram shows a fairly complex setup with a reference voltage that would probably require an IC anyway, so I don't there's much to gain by removing a chip if it requires another chip in addition to some discrete parts.
> Brian
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