Ever find yourself asking "How can I protect my Mega while providing some more secure connections?"
I was asked just that recently - so I came up with the Hardened Screw Shield.
Designed to plug onto your Mega and provide:
5.1V zener protection on every IO pin
Digikey BZX84C5V1W-FDICT-ND
30mA PTC protection on every screw terminal pin (can't intercept the header pins as they are pass thru), with holes to bypass the PTC at every screw terminal if desired.
Digikey 490-2470-1-ND
5V, 1A, PTC protected supply, provides power to the screw terminal and the Mega thru the 5V header with a diode to protect the Mega regulator. MC7805CT-BP used. Up to 35V input.
3.3V, 400mA supply, provides power to the screw terminal independent of the Mega. IFX25001 ME V33 used.
In addition, for another $9/card the 5V TO-220 package regulator can be replaced with this 6.5V-32V input to 5V output Recom switching regulator instead, I would just need to know ahead of time.
As you can see, this is a lot of components on the board - 209!
I've priced up a 10-lot with all material and an estimated assembly cost by CBAS-USA.inc in CA. If I can get commitments for 10 of these, the price each can be $168 including flatrate mailing to your US location, foreign another $4-5 more.
I think I have a takers for 5 of them already - but a 5-lot doesn't distribute the $400 in assembly set up costs enough, makes it $214, so I'm really shooting for 10 or more.
It also occurred to me that I could make it available without the screw terminals - but that really just provides the benefit of the zeners, as the 30mA PTCs are between the header and screw terminals.
Or perhaps just have CBAS quote doing the SMD parts, and leave the rest in kit form like the Mega screw shield. That could help bring the price down too, and puts the kitting effort back in my hands.
Too many options.
Any takers? It nothing else, it was a fun design exercise.
