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Feb 28, 2017, 12:45 PM
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LittleMo's Avatar
Question

How much current on +5V serial port of Multi4?


The Multi4 has a 3-pin serial port connector with ground, +5V, and signal. How much current can the +5V connector supply?

Thanks!
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Mar 01, 2017, 06:02 AM
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ggcrandall1's Avatar
Quote:
Originally Posted by LittleMo View Post
The Multi4 has a 3-pin serial port connector with ground, +5V, and signal. How much current can the +5V connector supply?

Thanks!
That port is for power to the FUIM3 data cable. I doubt you can use it to power anything else.

Glen
Mar 01, 2017, 07:04 AM
Registered User
Quote:
Originally Posted by ggcrandall1 View Post
That port is for power to the FUIM3 data cable. I doubt you can use it to power anything else.

Glen
That is correct. It will only provide a few mA and the voltage drops quickly with load.
Mar 01, 2017, 08:08 AM
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LittleMo's Avatar
I know what it's for but that wasn't my question. How much is a "few" mA?

Edit:
Briefly looking at the circuit it looks like that might be the main 5V power rail for the whole device in which case it seems likely it can supply a reasonable amount of power. I can't find a good picture of the board online and I don't really want to dissemble the whole thing to find out where the regulator is which is why I was asking before resorting to such methods.

Edit again:
Looks like LM78L05ACM so 100mA total supply. Not sure what the charger (display, etc) draws though so not sure how much current is left over.
Last edited by LittleMo; Mar 01, 2017 at 08:29 AM.
Mar 02, 2017, 08:37 PM
Registered User
Quote:
Originally Posted by LittleMo View Post
I know what it's for but that wasn't my question. How much is a "few" mA?

Edit:
Briefly looking at the circuit it looks like that might be the main 5V power rail for the whole device in which case it seems likely it can supply a reasonable amount of power. I can't find a good picture of the board online and I don't really want to dissemble the whole thing to find out where the regulator is which is why I was asking before resorting to such methods.

Edit again:
Looks like LM78L05ACM so 100mA total supply. Not sure what the charger (display, etc) draws though so not sure how much current is left over.
It is only tested to support about 10mA which is required by the FUIM.


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