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Forum Index : Microcontroller and PC projects : voltage on 5 V pins
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| hitsware Guru  Joined: 23/11/2012 Location: United StatesPosts: 535 |
~ what should the 5 V pins read if running off usb ? I accidently shorted the 5 V to Gnd for a short (less than a sec) I now read ~ 4 V, (3.3 is right on) but my DuinoMite reads ~ 4.75 V It seems lower than before but ? (some op amps act differant than before (but I hadn't actually measured)) |
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BobD Guru Joined: 07/12/2011 Location: AustraliaPosts: 935 |
what device are we talking about, MM, CMM, DM etc.? Have you changed the usb cable? Tried to a different usb port on the PC? |
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| hitsware Guru Joined: 23/11/2012 Location: United StatesPosts: 535 |
> what device are we talking about, MM, CMM, DM etc.? CMM > Have you changed the usb cable? Yes > Tried to a different usb port on the PC? Yes. Also tried differant PC measured 0.6 V accross the Shockey diode which is what it should be @ ~ 1 Amp ? nothing seems hot |
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Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3165 |
You should only get a voltage drop of 0.3V across the Shockey diode. The minimum USB voltage spec is 4.5V so your 5V rail could get as low as 4.2V. Geoff Geoff Graham - http://geoffg.net |
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| hitsware Guru Joined: 23/11/2012 Location: United StatesPosts: 535 |
Thanks ! Could I have stressed it into the higher drop when I grounded the 5V line ? |
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| Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3165 |
No, that does not sound likely, the 1N5819 is a 1 Amp diode and most USBs are limited to about 0.5A. You could check that the diode is actually a 1N5819 as other diodes can have a higher voltage drop. Geoff Graham - http://geoffg.net |
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