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Korad KA3005P outputs less then set?
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VenHeelun:
Hi

I do understand a very little about electronics but i still did buy a Korad KA3005P to do some small projects.
I did buy a ledstrip & controller about one year ago and want to see if they work.
The controller is a SP108E Wifi controller witch can be operated with a phone.
The ledstrip is a 5mtr UCS1903 rgb ledstrip witch is adressable per led.

The SP108E: DC5V - 24V, 20mA - 130mA
The UCS1903 ledstrip: DC12V, 14,4W/Mtr (so total 72W / 6A)

Q1:
If i set the powersupply to 12V at 1A (witch is to low) then the voltage is only ouputting 9.5V.
At 5A (the highest on the powersupply) it outputs 12V, 2,1A.
Why 9,5V on 1A? That's 2,5V lower.

Q2:
Can i connect both controller (130mA) & ledstrip (6A) on one 12V, 6A powersupply?
Can i damage anything (on the controller) this way?

Thank you
ataradov:

--- Quote from: VenHeelun on January 10, 2019, 07:25:15 pm ---If i set the powersupply to 12V at 1A (witch is to low) then the voltage is only ouputting 9.5V.
At 5A (the highest on the powersupply) it outputs 12V, 2,1A.
Why 9,5V on 1A? That's 2,5V lower.

--- End quote ---
Power supply enters into constant current mode, so it start to lover the voltage until current consumption is at the set level.

Clearly your device consumes 2.1V. So any current limit setting will result in a reduced voltage.


--- Quote from: VenHeelun on January 10, 2019, 07:25:15 pm ---Can i connect both controller (130mA) & ledstrip (6A) on one 12V, 6A powersupply?
Can i damage anything (on the controller) this way?

--- End quote ---
Yes, 130 mA is an insignificant additional load, it should not cause any harm.
tooki:

--- Quote from: ataradov on January 10, 2019, 08:00:25 pm ---
--- Quote from: VenHeelun on January 10, 2019, 07:25:15 pm ---If i set the powersupply to 12V at 1A (witch is to low) then the voltage is only ouputting 9.5V.
At 5A (the highest on the powersupply) it outputs 12V, 2,1A.
Why 9,5V on 1A? That's 2,5V lower.

--- End quote ---
Power supply enters into constant current mode, so it start to lover the voltage until current consumption is at the set level.

Clearly your device consumes 2.1V. So any current limit setting will result in a reduced voltage.

--- End quote ---
You mean 2.1A, right? And thus that any current limit setting below 2.1A will result in reduced voltage.
ataradov:
Yes, just a spelling error
tooki:

--- Quote from: VenHeelun on January 10, 2019, 07:25:15 pm ---Hi

I do understand a very little about electronics but i still did buy a Korad KA3005P to do some small projects.
I did buy a ledstrip & controller about one year ago and want to see if they work.
The controller is a SP108E Wifi controller witch can be operated with a phone.
The ledstrip is a 5mtr UCS1903 rgb ledstrip witch is adressable per led.

The SP108E: DC5V - 24V, 20mA - 130mA
The UCS1903 ledstrip: DC12V, 14,4W/Mtr (so total 72W / 6A)

Q1:
If i set the powersupply to 12V at 1A (witch is to low) then the voltage is only ouputting 9.5V.
At 5A (the highest on the powersupply) it outputs 12V, 2,1A.
Why 9,5V on 1A? That's 2,5V lower.

--- End quote ---
The key to remember is that the voltage and current settings are limits. (You cannot force a certain current through something. Ohm's law explains the relationship of how a voltage "pushes" current through a load.) And the voltage limit takes priority over the current limit. (For the sake of understanding, pretend that without the setting, the power supply would output infinite voltage. So the setting keeps it down where we need it.)

So when you set the power supply to 12V/1A, what you're saying is "do not exceed 12V, AND do not exceed 1A". Since the voltage's primary control is the setting, then it will remain at 12V, unless the current limit (1A here) is exceeded, in which case the current limiting kicks in and takes over, lowering the voltage until the current limit is no longer exceeded. Note that at any given time, EITHER the voltage limit OR the current limit is in control, but not BOTH at the same time! This is what the CV and CC* lights on the power supply indicate: which limit is in control right now!

*Meaning "constant voltage" and "constant current", though those names are IMHO not very good, but they're what the industry uses. I think "voltage-limited" and "current-limited" would be better, but lab PSUs tend to use "limit" to mean turning off once a limit is breached.
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