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| MarkF:
You have a little design work and choices to make here. The 1N400x series diodes are rated for 1A. While the 1N539x series are 1.5A but their forward voltage drop is greater. You might look at a full wave bridge module instead of individual diodes. Your choice. The capacitor choice depends on voltage drop/ripple, line frequency and current. Here is a pretty good video on choosing the values: https://youtu.be/CAYKno16weE |
| Pirateguy:
i like to use what i have, and i don't need the rectifier part if i'm using a DC source like the HP supply, do i? but there are 2 more diodes to the right, i was thinking of those. in any case my poly fuses are 0.9A so i guess these will do. |
| Pirateguy:
i i watched the video and followed the math, and i end up with a 10uf cap. so i am guessing that corresponds to the 10uf cap in the circuit, but i was thinking of the 6800 one. |
| MarkF:
--- Quote from: Pirateguy on August 30, 2018, 07:59:13 pm ---i like to use what i have, and i don't need the rectifier part if i'm using a DC source like the HP supply, do i? but there are 2 more diodes to the right, i was thinking of those. in any case my poly fuses are 0.9A so i guess these will do. --- End quote --- The two diodes on the right side are protection diodes. They are for reverse-voltage and over-voltage being applied to the outputs. You want those and you could use your 1N400x series diodes there. You're right. You don't need the rectifier if you feed a DC voltage into the regulator. And the input capacitor can be small. I'd use something like 100uF. The video is not applicable if you feed the regulators with a DC voltage. The maximum input voltage of the MC98xx regulators is 35V. If you intend to use your 32VDC supply to feed 5V and 12V regulators, the power dissipation of the regulators will be enormous. They will get very very very hot! You want an input voltage to the regulators 5-10V above their output voltage to minimize the power they will need to dissipate. Don't forget their drop out voltage is 2V. I DO NOT think your 32VDC power supply is an appropriate choice. If you want to build this, I highly recommend you use the bridge rectifier and obtain the appropriate sized transformer for each. |
| Pirateguy:
--- Quote ---The maximum input voltage of the MC98xx regulators is 35V. If you intend to use your 32VDC supply to feed 5V and 12V regulators, the power dissipation of the regulators will be enormous. They will get very very very hot! You want an input voltage to the regulators 5-10V above their output voltage to minimize the power they will need to dissipate. Don't forget their drop out voltage is 2V. I DO NOT think your 32VDC power supply is an appropriate choice. If you want to build this, I highly recommend you use the bridge rectifier and obtain the appropriate sized transformer for each. --- End quote --- seriously? after 5 pages of discussion, diagrams and shopping advice, you are basically telling me to shove a 5v and a 12v wallwart into a box and call it a project? if i happen to have a wallwart for every voltage i want, do i still need the regulators? |
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