[chbot] 12V driver

[Mark Atherton]

However you mix IO and switched loads, and regardless of hi or lo side 
switching, it is important to understand the ground loop associated with 
the load side.

It is good practice to elect a single ground point for such situations, 
usually at the ground reference pin of the power switching device. It is 
at this point you dive down the rabbit warren of analogue electronics.

One easy way to avoid this whole mess is to isolate the switching device 
(and associated power supply) from the load (and associated power supply).

... or use a relay !

- Mark




On 24/05/2021 6:35 PM, Charles Manning wrote:
> L293DD looks like a very elegant solution.
> 
> ULN2003 is a low side driver. Careful using these... If you're just 
> using it to switch on a load without any other IO (or completely 
> isolated IO then they're OK. But if you're switching on anything that 
> has IO wires then low side switching is bad, bad, bad because the 
> switched device will try to find ground via IO wires causing problems.
> 
> 
> On Mon, May 24, 2021 at 1:14 PM hamster at snap.net.nz 
> <mailto:hamster at snap.net.nz> <hamster at snap.net.nz 
> <mailto:hamster at snap.net.nz>> wrote:
> 
>     I have been using L293DD. Up to 32V and 600mA, and seperate 4
>     channels in easy SMD package.
> 
>     I have a few spare and a suitable PCB to drive 16 channels of LED
>     lights if you want to experiment. It has a Pi Pico footprint on it
>     but that isn't a big issue.
> 
>     The PCB is useful as the need to sink a bit of heat into the PCB's
>     ground plane.
> 
>     Mike
> 
> 
> 
> 
>     -------- Original message --------
>     From: Mark Atherton <markaren1 at xtra.co.nz <mailto:markaren1 at xtra.co.nz>>
>     Date: Mon, 24 May 2021, 12:34 PM
>     To: Christchurch Robotics <chchrobotics at lists.linuxnut.co.nz
>     <mailto:chchrobotics at lists.linuxnut.co.nz>>
>     Subject: [chbot] 12V driver
> 
>         Andrew,
> 
>         After all that I forgot...
> 
>         ULN2003 - seven drivers in a 16 pin DIP, Jaycar ZK8855, $5.90 ea.
> 
>         5V in, capable of switching 500mA at 50V. Built in back EMF
>         diode (tie
>         pin 9 to the positive rail associated with the load).
> 
>         -Mark
> 
> 
> 
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