- #1
Shadrack
- 15
- 0
Wow! An Electrical Engineering Forum! :!)
Please help!
I'm a newbie in the field, just got my degree last May (2005, BSEE). I focussed on computer engineering and can program the crap out of a micro-controller. Now I'm working on some automated test systems and have to work on a lot of other people's poorly documented work.
My electronics know how is very rusty, and my power management know how is non-existent. Ok, enough with my intro...onto a few questions:
1.
What do I do with multiple power supplies in a system? The system that I am currently having a lot of problems with atm has 3 power supplies throughout the entire system . They are all DC: 1x 5V, 2x 12V. What should I do with ground? Should I just connect all the grounds together? I measure about a 1mV difference between the different ground planes... connecting them together causes a small amount of current, should I be concerned? What is the best way to inner-connect multiple power-supplies throughout a system? The components are not optically isolated from each other.
For instance, the output of one module is a 5V DC signal, and the module is being powered by the 5V power supply. The signal goes into a series of Inverter units that is powered b a 12V power supply to bounce the signal around between 0V and 12V. ? this seems very problematic to me unless the inverter units are optically isolated which they don't appear to be.
Wouldn't it be better to use 1 DC power supply at the highest voltage rating that is needed in the system and could deliver enough current to everything, then use DC-DC converted and voltage regulators to take care of the small stuff? How do you manage your power?
Any good references on system power management? I'm just using basic P=I*V and keeping track of my currents going between modules.
2.
Is there anything wrong with using a voltage divider to bring 24V down to ~5V to feed a 3.3V regulator? What "level" of resistors should i use? High resistors will lower power usage, so it seems to me I should use those.
3.
Why is there a small amount of resistance between the + and - terminals of my power supplies. Only a couple hundred of ohm (not connected to anything else). Intuition tells me there should be a HIGH amount of resistance between the terminals. Then again "low output impedance, high input impedance" is ringing in my head. But for a power supply?? Wouldn't there be a lot of internal current flowing between those two potentials with such a low resistance between the two? What is going on here?
4.
O.T.: can anyone recommend a good IDC connector crimp tool?
Thank you for your input!
BTW: love all the emoticons on this forum...very appropriate.
-Shadrack
Please help!
I'm a newbie in the field, just got my degree last May (2005, BSEE). I focussed on computer engineering and can program the crap out of a micro-controller. Now I'm working on some automated test systems and have to work on a lot of other people's poorly documented work.
My electronics know how is very rusty, and my power management know how is non-existent. Ok, enough with my intro...onto a few questions:
1.
What do I do with multiple power supplies in a system? The system that I am currently having a lot of problems with atm has 3 power supplies throughout the entire system . They are all DC: 1x 5V, 2x 12V. What should I do with ground? Should I just connect all the grounds together? I measure about a 1mV difference between the different ground planes... connecting them together causes a small amount of current, should I be concerned? What is the best way to inner-connect multiple power-supplies throughout a system? The components are not optically isolated from each other.
For instance, the output of one module is a 5V DC signal, and the module is being powered by the 5V power supply. The signal goes into a series of Inverter units that is powered b a 12V power supply to bounce the signal around between 0V and 12V. ? this seems very problematic to me unless the inverter units are optically isolated which they don't appear to be.
Wouldn't it be better to use 1 DC power supply at the highest voltage rating that is needed in the system and could deliver enough current to everything, then use DC-DC converted and voltage regulators to take care of the small stuff? How do you manage your power?
Any good references on system power management? I'm just using basic P=I*V and keeping track of my currents going between modules.
2.
Is there anything wrong with using a voltage divider to bring 24V down to ~5V to feed a 3.3V regulator? What "level" of resistors should i use? High resistors will lower power usage, so it seems to me I should use those.
3.
Why is there a small amount of resistance between the + and - terminals of my power supplies. Only a couple hundred of ohm (not connected to anything else). Intuition tells me there should be a HIGH amount of resistance between the terminals. Then again "low output impedance, high input impedance" is ringing in my head. But for a power supply?? Wouldn't there be a lot of internal current flowing between those two potentials with such a low resistance between the two? What is going on here?
4.
O.T.: can anyone recommend a good IDC connector crimp tool?
Thank you for your input!
BTW: love all the emoticons on this forum...very appropriate.
-Shadrack
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