Re: neat Hall sensor

On a sunny day (Thu, 02 Jan 2025 07:54:43 -0800) it happened john larkin
<JL@gct.com> wrote in <vgddnjdm1rg7u1fj7p7o5d66v7je0b9c04@4ax.com>:

On Thu, 02 Jan 2025 13:01:42 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
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On a sunny day (Wed, 01 Jan 2025 08:02:29 -0800) it happened john larkin
<JL@gct.com> wrote in <b0panjdbtuk2648jf9b2pe85sg65jqalsd@4ax.com>:
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On Wed, 01 Jan 2025 08:11:06 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
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On a sunny day (Tue, 31 Dec 2024 15:58:07 -0800) it happened john larkin
<jl@glen--canyon.com> wrote in <nm09njhfcjh49jbof7qm3fl8pv321j34sk@4ax.com>:
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https://www.monolithicpower.com/en/mcs1802.html?srsltid=AfmBOoq2BNuYQ-Ef5ee9o7-gyHDqRkK_xS5TAKb-MgxtjZ6r71FItxXm
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Really nice, as compared to a shunt and an isolated ADC and all that
stuff. Reasonably accurate, especially above 20c.
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But they can't be serious about pushing 50 amps through an SO8
package. Or not for long.
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Their demo board thermal design is kinda silly.

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I use some of these:
https://www.lem.com/en/product-list/hx-10p
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Maybe they have 50 amp versions too?

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We have a LEM HMSR6-SMS instock... not sure why. There is a 30 amp
version. It's more accurate than the Monolithic part and has nice
chunky current leads, but it costs over 2x as much as the Mono part.
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https://www.digikey.com/en/products/detail/lem-usa-inc/HMSR-6-SMS/12686318?s=N4IgTCBcDaIBIFkDKAlAbAWickBdAvkA
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We can auto-zero the Monolithic part at powerup, which will help the
accuracy a bit.
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I'm designing a plugin to our modular power system, just a board with
eight power relays. Then we figured, let's measure the voltage and
current of each relay too. Featuritus follows. Why not make it a
programmable circuit breaker? Why not a polyphase wattmeter? Somebody
please stop me.

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Long time ago I used an old tape recorder head as AC current sensor:
https://panteltje.nl/pub/play_back_head_current_sensor_img_1153.jpg
needs some amplification, rectifier.. so an opamp + diode.
But AC only.. but will work with more than 60 Hz, few dollars on ebay..

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For sensing AC current, one could use a milliohms-range 1206 resistor
and a signal transformer, a DRQ127 maybe. That all costs about a
dollar. All surface mount.

For cycle by cycle current limit purposes I use a simple ringcore
current transformer into a Microchip PIC comparator input:
 https://panteltje.nl/pub/sc2_pwr-0.3_diagram_img_3251.jpg
  ringcore is in drain power MOSFET, basically a simple current transformer,
  secondary must be loaded with a resistor.