JahJahBinks
Headphoneus Supremus
- Joined
- Nov 22, 2002
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This is for my school project. I have designed a digital circuit for my team and due to safety concern I would like to make sure it does not fail on the exhibition day. I think the three main reason for failure are 1) plugged in Vdd for GND and GND for Vdd. 2) reverse current 3) over-voltage, 4) over-current.
The first case can be prevented by checking the connection before turning the power supply on. The second case can be prevented by using Zener Diodes. However for the latter two cases I have to trust the power supply. If 20 something IC chips on my circuit all short out at once, or even one stops working then I will be really screwed.
So to prevent over-voltage I decided to over a voltage regulator (such as LM7805). My questions are: 1) Hooking input and output pins to capacitors can reduce the noise. What's the formula for calculating the cutoff frequency? It behaves like a low pass filter, right? 2) Extra voltage is transformed into heat, but if I use a 5v voltage regulator and it receives 5v from power supply over a long period of time, do I need to attach a heat sink to it?
If you have better idea in prevent over-voltage, please tell me. As for over-current, I am not sure if that's a major problem or not, I need your two cents. Thank you!
The first case can be prevented by checking the connection before turning the power supply on. The second case can be prevented by using Zener Diodes. However for the latter two cases I have to trust the power supply. If 20 something IC chips on my circuit all short out at once, or even one stops working then I will be really screwed.
So to prevent over-voltage I decided to over a voltage regulator (such as LM7805). My questions are: 1) Hooking input and output pins to capacitors can reduce the noise. What's the formula for calculating the cutoff frequency? It behaves like a low pass filter, right? 2) Extra voltage is transformed into heat, but if I use a 5v voltage regulator and it receives 5v from power supply over a long period of time, do I need to attach a heat sink to it?
If you have better idea in prevent over-voltage, please tell me. As for over-current, I am not sure if that's a major problem or not, I need your two cents. Thank you!