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Switching an unknown DC voltage with a LVTTL signal
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hamster_nz:
What is a good way to switch an known DC voltage (between 2.4V and 24V) with unknown polarity using a 3.3V CMOS logic signal? The controlled signal will usually be driving low voltage DC motors. If the polarity was known I would just use a logic level MOSFET.
A relay would be the ideal, but energizing it uses too much power - I want to drive it for many hours from a CR2032 cell.
langwadt:
--- Quote from: hamster_nz on June 24, 2020, 10:07:23 pm ---What is a good way to switch an known DC voltage (between 2.4V and 24V) with unknown polarity using a 3.3V CMOS logic signal? The controlled signal will usually be driving low voltage DC motors. If the polarity was known I would just use a logic level MOSFET.
A relay would be the ideal, but energizing it uses too much power - I want to drive it for many hours from a CR2032 cell.
--- End quote ---
if you supply is isolated, back-to-back mosfets?
or maybe a latching relay?
hamster_nz:
--- Quote from: langwadt on June 24, 2020, 10:29:50 pm ---if you supply is isolated, back-to-back mosfets?
--- End quote ---
Supply is definitely isolated (battery powered device). So something like this attached schematic?
Hummm - can't see how I would reference the 'smart switch' to the load being switched...
langwadt:
--- Quote from: hamster_nz on June 24, 2020, 10:57:52 pm ---
--- Quote from: langwadt on June 24, 2020, 10:29:50 pm ---if you supply is isolated, back-to-back mosfets?
--- End quote ---
Supply is definitely isolated (battery powered device). So something like this attached schematic?
Hummm - can't see how I would reference the 'smart switch' to the load being switched...
--- End quote ---
basically this: https://www.homemade-circuits.com/wp-content/uploads/2020/01/SSR-concept.png
the two sources are "ground" for your control circuitry
hamster_nz:
--- Quote from: langwadt on June 25, 2020, 02:34:58 pm ---
--- Quote from: hamster_nz on June 24, 2020, 10:57:52 pm ---
--- Quote from: langwadt on June 24, 2020, 10:29:50 pm ---if you supply is isolated, back-to-back mosfets?
--- End quote ---
Supply is definitely isolated (battery powered device). So something like this attached schematic?
Hummm - can't see how I would reference the 'smart switch' to the load being switched...
--- End quote ---
basically this: https://www.homemade-circuits.com/wp-content/uploads/2020/01/SSR-concept.png
the two sources are "ground" for your control circuitry
--- End quote ---
Perfect. Thanks for your help.
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