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| Connecting the grounds of two power supplies | ||
| Author edu Views 8 Posted at 2008/8/27 20:13 [View In Forum] | ||
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HIuwcu uwcu uwcu uwcu Can the grounds of two different power supplies each supplying different voltages be connected?uwcu uwcu uwcu uwcu If not, why?uwcu uwcu uwcu uwcu And if they can...uwcu uwcu uwcu uwcu what about the theory of isolation? For instance in the case where a microprocessor operating at 5V is connected to a device using 240V, the have to be isolated from each other? |
| Reply No. | Replier | Total Replies 6 [View All Replies] [New Reply] | Replied at |
| 1 | yvling | Yes the two grounds can be connected to each other, but both should be DC voltages | 2008/8/27 20:13 |
| 2 | anuo2008 | I am not aware of any standard that will prevent you from connecting grounds of different power supplies .. Of course, you have to implement safety precautions not to expose users to dangerous high voltages .. As an example have a look at light dimmers, touch-button light switches (here you touch mains through some MΩ resistor) etc. etc. They have mixed low and high voltage ground and to keep their size small, no isolation transformers or optocouplers are used .. However, my advice is that whenever it is possible always use proper isolation .. Regards, IanP |
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| 3 | wyslnhhh56 | With DC power supplies this is usually not a problem and sometimes a requirement. Keep in mind though with the proliferation of switch mode power supplies simply connecting the ground of two power supplies may cause strange side effects as it's a way for the ripple to interact inbetween units when they're under curent draw. As far as 5 volts vice 240V's... Common sense should kick in at some point. A 240 V power supply with normal wireing while under load is going to draw some pretty impressive pulse wattage and gonna screw with the 5 volt side pretty badly. Meanwhile if you're drawing high current on the 5 volt side it may likewise cause voltage fluctuations on the 240v side. No wireing is a perfect ground so things will always flluctuate, it's mostly a matter of how much current you're drawing. All sorts of unwantted reactions could take place. For common electronics applications it's generally safe to use a common ground for things like multiple power supplies in the range of -12 to 12 volts or so, the less current you're dealing with the better. What worries me is it sounds like you're using rectified mains voltage and logic voltage totally un issolated from each other.... bad idea. Lots of smoke and melted metal possibilities =) | 2008/8/27 20:13 |
| 4 | ken7976 | isolation is very necessary & ur appllications will run properly only if u have connected the grounds of two or more circuits for which the 'voltage level' to recognize the ground is same otherwise u can make damage | 2008/8/27 20:13 |
| 5 | fujun2013 | hi:idea: To isolate a digital source From a Uc you can use OPTO coupller. To isolate a sine wave you can a transformer easily. To isolate an analoge source , use this method ................VCO ............OPTO.............filter or PLL..................... analoge -------->Freq. ---------->Freq. ------------->analoge ................................................................................................ |
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| 6 | ct731 | 2008/8/27 20:13 | |
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