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Grogster

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Joined: 31/12/2012
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Posted: 02:39pm 05 Oct 2017

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@ vegipete and Andrew_G - Time for the HC12 to reinitalize is 200mS, so from power-up to first byte, you have to wait that long. I opt for 250mS to be sure. The SET pin can be left floating, as it has an internal pull-up on-board to the HC12's on-board 3v3 regulator voltage.(is normally 3v3 if you measure across SET and GND)

Smoke makes things work. When the smoke gets out, it stops!

Andrew_G
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Joined: 18/10/2016
Location: Australia
Posts: 871

Posted: 07:57pm 05 Oct 2017

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The things that are holding me up from a breadboard test bed are:
- a through hole equivalent of Captain Boing's BS250 (as he foresaw - not easy to find)
- through hole equivalents of Grogster's SMD FMMT493 and DMP2305 (I was thinking I could solder wire legs onto them - I have my wonderful microscope . . .?)

Cheers, Andrew

Grogster

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Posted: 10:35pm 05 Oct 2017

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If you are looking for through-hole versions, I would simply go for a BC548 or perhaps a BC337 etc for the NPN transistor, and any suitable P-MOSFET in TO-92 or TO-220.

With the MOSFET, the only things you need to be careful of is the Vgs(max volts between gate and source) and Vsd(max volts between source and drain)

The Vgs needs to be at least a few volts above the maximum you plan to power the switched device from. In the case of an HC12, you only need a MOSFET that is happy with a 5v Vgs or so, and many MOSFET's support that.

Smoke makes things work. When the smoke gets out, it stops!

disco4now

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Joined: 18/12/2014
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Posts: 1003

Posted: 10:39pm 05 Oct 2017

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I use upside veroboard to mount these small SMDs so I can add them to prototypes. Below is that NPN + FET circuit plus a voltage reference. Just cut one track and the three legs mount easily straddling the two adjacent tracks and the cut. Just solder some header pins flush where you want to connect to host board.

Gerry

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Andrew_G
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Posted: 09:55am 06 Oct 2017

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Disco - perfect, thanks. Andrew

Grogster

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Posted: 06:44pm 06 Oct 2017

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Yes, that is very crafty Disco.

Smoke makes things work. When the smoke gets out, it stops!

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