(chiming music)
- [Instructor] Alright folks, it's time
for a challenge problem.
This is your chance to practice
using diodes to protect a circuit.
For this challenge, I want you to determine
how to use diodes to ensure that the thermostat
in my house remains powered.
I'm going to be going on vacation for a few days
and I'll be leaving my pet hamster at home alone.
So, I want to guarantee that the temperature in the house
will be comfortable for him while I'm gone.
In this scenario, it's critical that my thermostat
always has uninterrupted DC power.
So, for redundancy, I've connected
two DC power supplies in parallel.
Each of these can individually power the thermostat.
So, if one supply fails, the other will pick up slack,
and my thermostat will never notice.
All electronic components have the potential
to fail and stop working.
And with my luck, it usually happens
at the worst possible time.
So, for critical applications like this,
I need to consider how my power supplies can possibly fail.
In general, they could fail in one of two ways.
The component inside the power supply might break
in a way that disconnects the power supply,
so it acts like an open circuit.
That's usually the safest way for a device to fail.
Or, if I'm really unlucky, the component inside
might overheat and melt together to create a short circuit.
That short circuit scenario
is the one I'm most worried about.
If one of my DC power supplies failed
and turned into a short circuit,
current from the surviving supply would go through
that short circuit instead of to the thermostat.
So, I lose power.
And even worse, the high current draw from the short circuit
would likely overload that second power supply
and cause it to break as well.
So, I need a way to protect my system
from that potential disaster.
Your goal for this challenge, is to determine
how to use diodes to protect my system
in case either of the DC power supplies fails,
and internally short circuits.
You'll need to determine the type of diodes to use
and where they should be placed in the system.
Take some time to think through this challenge.
And when you're done, be sure to watch my solution video
to see how I approached the problem.