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Greetings:
I recently made my first prototype surface mount board. In designing it, all the SMT components were foriegn to me. I'm a ME, not and EE and my projects are fairly straightforward microprocessor based designs. I chose components similar to old standbys I've used with through hole designs.
I needed to have a uP "wake on change" from one of 2 switch presses. I had 3 available inputs and only one of those had the wake on change feature.
So, I used a pair of diodes to "share" the single wake on change pin withthe switches, and tied each switch to the other 2 pins. When a switch is pressed, it signals the wakeup pin (via one of the diodes), and it's own pin. The diode prevents the current from passing to the other switch's pin. The uP wakes, then polls the switch pins to see which of the 2 woke it up.
I need an inexpensive diode for this job. There won't be any significant current through this, only the leakage current on the uP pin I think. The switch's ground a pulled-up uP line. It's a 3V (2 AAA batteries) powered, the pullups are 100k. When a switch is depressed it changes the shared pin from pulled up 3V, to grounded.
It all works fine but I initially chose a S1A diode from Fairchild (SMA package). When it arrived I found the SMA is large and bulky compared to my other components, overkill at 1A 50V.
Can someone recommend a good, inexpensive diode for this job. I would prefer it be:
a) smaller
b) cheap or as cheap
c) low V drop so a low battery can still show a "high" on the shared pin after the V drop through the diode.
Thanks!
Greg
I recently made my first prototype surface mount board. In designing it, all the SMT components were foriegn to me. I'm a ME, not and EE and my projects are fairly straightforward microprocessor based designs. I chose components similar to old standbys I've used with through hole designs.
I needed to have a uP "wake on change" from one of 2 switch presses. I had 3 available inputs and only one of those had the wake on change feature.
So, I used a pair of diodes to "share" the single wake on change pin withthe switches, and tied each switch to the other 2 pins. When a switch is pressed, it signals the wakeup pin (via one of the diodes), and it's own pin. The diode prevents the current from passing to the other switch's pin. The uP wakes, then polls the switch pins to see which of the 2 woke it up.
I need an inexpensive diode for this job. There won't be any significant current through this, only the leakage current on the uP pin I think. The switch's ground a pulled-up uP line. It's a 3V (2 AAA batteries) powered, the pullups are 100k. When a switch is depressed it changes the shared pin from pulled up 3V, to grounded.
It all works fine but I initially chose a S1A diode from Fairchild (SMA package). When it arrived I found the SMA is large and bulky compared to my other components, overkill at 1A 50V.
Can someone recommend a good, inexpensive diode for this job. I would prefer it be:
a) smaller
b) cheap or as cheap
c) low V drop so a low battery can still show a "high" on the shared pin after the V drop through the diode.
Thanks!
Greg
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