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PTT Output
Posted: Thu Jan 04, 2018 11:09 am
by G4uvz
I am sure it is in the Wiki!!! Please can you ell me how much current the PPT can sink? do you need a back emf diode ? I am assuming that any load is connected between the PTT switch and HT ..12 volts?
Re: PTT Output
Posted: Thu Jan 04, 2018 1:56 pm
by M5TXJ
As in the wiki, 60V max, 2 Ohms max on resistance, 500mA max. As you're using a semiconductor switch I'd say a back emf diode will be essential.
73 Dave
Re: PTT Output
Posted: Thu Jan 04, 2018 3:28 pm
by MN-tech
As is often the case you need to read further than the absolute maximums in the datasheet and look at combinations of conditions. 400 mw is the maximum power dissipation based on an ambient temperature of 25 degrees C. If the current is the max of 500 ma and the resistance is the max of 2 ohms the power dissipation would be 1000 mw. In actual use it would be prudent not to exceed 200 ma which still is more than enough for a couple of 12 volt relays.
Re: PTT Output
Posted: Thu Jan 04, 2018 4:07 pm
by G4uvz
Thanks for the comments...not having used optos before ..I assume that they are polarity conscious?
Adrian
Re: PTT Output
Posted: Thu Jan 04, 2018 5:04 pm
by MN-tech
The TLP222A is not polarity sensitive, use it like you would a relay contact. You could even switch AC with it.
Re: PTT Output
Posted: Thu Jan 04, 2018 6:07 pm
by G4uvz
Excellent Thank you!