Received My Korad - Page 1
Forum section: electronics / beginners

author: tony3d
author_rank: Frequent Contributor
timestamp: September 26, 2013, 09:00:30 pm
content: Just had my Korad delivered, and have a couple questions.1. Set to 7 volts, and using a red LED and 1007k resistor, I' getting .003mA on the power supply, and 5.10mA on my meter. Is this in expectable performance for this supply? Everything seems to work fine. I'm just starting out learning so pardon my ignorance about what performance to expect. The volts at any reading are almost right on or to within .02 worst case from 0-31v.

author: Unknown
author_rank: Unknown
timestamp: September 26, 2013, 09:06:13 pm
content: That's 0.003 A, or 3 mA on the power supply. Since this is at the very bottom of the scale for the power supply, 2 mA error (assuming the meter is spot on) is acceptable performance in my opinion. The spec will probably allow for a few mA error.

author: tony3d
author_rank: Frequent Contributor
timestamp: September 26, 2013, 09:10:39 pm
content: So you feel this would be normal then?

author: wraper
author_rank: Unknown
timestamp: September 26, 2013, 09:11:41 pm
content: It is showing 0.003A, not mA. This is within spec because meter has tolerance % + couple of digits. I didn't bother to find exact specifications because all digital meters have such a thing. Check how it performs with a bigger load.

author: tony3d
author_rank: Frequent Contributor
timestamp: September 26, 2013, 09:12:38 pm
content: Set to 1 volt and 5.000 amps I'm getting 4.365 directly in the meter. Is this because of the lead resistance?

author: wraper
author_rank: Unknown
timestamp: September 26, 2013, 09:15:21 pm
content: Should be, leads are thin and crappy + some shunt resistance.

author: TopLoser
author_rank: Unknown
timestamp: September 26, 2013, 09:19:58 pm
content: Set PSU to CC 5.00A instead of CV 1.00V , and if your meter is within a few digits then I'd be happy your PSU is ok.

author: tony3d
author_rank: Frequent Contributor
timestamp: September 26, 2013, 09:20:30 pm
content: They really are. Think I'll order some good leads from Franky on ebay. He has a nice set of 14 AWG leads for $9.95. Nice banana plugs as well. I guess it's all working pretty well. I'm happy so far. Hope it lasts.

author: tony3d
author_rank: Frequent Contributor
timestamp: September 26, 2013, 09:21:44 pm
content: Quote from: TopLoser on September 26, 2013, 09:19:58 pmNot sure how to do that. Never owned one of these before.

author: tony3d
author_rank: Frequent Contributor
timestamp: September 26, 2013, 09:29:54 pm
content: Ok, If I raise the voltage to 1.5 it kicks into CC, and the power supply reads 4.996, my meter reads 4.98. Thats pretty good right?

author: wraper
author_rank: Unknown
timestamp: September 26, 2013, 09:31:18 pm
content: It is. There is voltage/current button BTW.

author: DavidDLC
author_rank: Frequent Contributor
timestamp: September 26, 2013, 09:39:41 pm
content: Measure the LED current without the DMM connected just the power supply, and then make the comparison as well.David.

author: tony3d
author_rank: Frequent Contributor
timestamp: September 26, 2013, 09:45:50 pm
content: Used a 47Ohm resistor to let more current flow, and now it's matching pretty well.

author: tony3d
author_rank: Frequent Contributor
timestamp: September 26, 2013, 10:13:08 pm
content: So do you think I got a pretty good one?

author: wraper
author_rank: Unknown
timestamp: September 26, 2013, 10:35:19 pm
content: I would say you got what should be expected.

author: tony3d
author_rank: Frequent Contributor
timestamp: September 27, 2013, 12:39:03 am
content: Really glad it arrived in perfect condition. Been playing with it for a few hours now, and so far no issues at all. Turned it on, and off a bunch of times, and the power switch seems solid, and working all right. Drew 5 amps off it for a while, and the unit remained pretty cool. Will have to buy good leads though. They heat up above 3amps.

author: iloveelectronics
author_rank: Frequent Contributor
timestamp: September 27, 2013, 12:57:01 am
content: Quote from: tony3d on September 27, 2013, 12:39:03 amHi Tony,If you were to order anything from my ebay store please do so in the next couple of hours as I will set the store on vacation mode after that. I will be away on holiday until the 8th. Do let me know if you miss it but still want something while I am away, I can try to get a family member to help out.Cheers,Franky

author: tony3d
author_rank: Frequent Contributor
timestamp: September 27, 2013, 11:55:33 am
content: Quote from: wraper on September 26, 2013, 09:31:18 pmI don't see a way to just set the supply to constant current. Voltage current button just switches between the two for setting. Seems if you increase the volts high enough,it will switch to CC on it's own, but I don't see a way to switch it, or set it on the fly. I got the OCP TO WORK FINE. So far I really like this unit. It's just the right size for my work area, and actually looks good cosmetically.

author: Unknown
author_rank: Unknown
timestamp: September 27, 2013, 12:01:25 pm
content: You don't set the power supply to constant current. You set a maximum current and voltage. If will limit either voltage (constant voltage) or current (constant current) to remain within these limits. Say you set the supply to 30 V, 1A. To supply 1 A to a 1 kOhm resistor would require 1 kV, so the supply limits the voltage to 30 V, which results in a current of much less than 1 A. If you now replace the resistor by a 1 Ohm resistor, 30 A would flow if the voltage were 30 V, so the supply limits the current to 1 A, resulting in a much lower voltage than 30 V.

author: tony3d
author_rank: Frequent Contributor
timestamp: September 27, 2013, 12:23:35 pm
content: I see. Thanks for that very clear explanation!

author: tony3d
author_rank: Frequent Contributor
timestamp: September 27, 2013, 03:21:33 pm
content: Ok, I'm really confused about the OCP, and OVP. I thought that both were to turn off the outputs of the supply when it reaches the limits you set. I can get it to work with the OCP by setting the high clamping point for the current with the output button off, then after turn on the output I press the OCP button. When I turn up the voltage, and the current reaches my preset value, the output is turned off. Now I thought the same should be true for the OVP, but I can't seem to get it to work. Any suggestions?

author: Electro Fan
author_rank: Super Contributor
timestamp: September 27, 2013, 03:49:22 pm
content: For what it's worth my Korad behaves the same way. I'm not clear on what Korad had in mind for the OVP button. I wouldn't worry too much about it but if you want to do some research you might contact Korad directly via email and see what they tell you. Let us know.

author: Andy Watson
author_rank: Super Contributor
timestamp: September 27, 2013, 05:00:19 pm
content: How are you expecting to obtain "over voltage" on what should be a regulated voltage output?

author: tony3d
author_rank: Frequent Contributor
timestamp: September 27, 2013, 05:05:17 pm
content: Quote from: Andy Watson on September 27, 2013, 05:00:19 pmSo I guess you just press the OVP button, and if a spike on the line comes along it clamps it. Is that what it's for?

author: Jonny
author_rank: Regular Contributor
timestamp: September 29, 2013, 08:56:43 am
content: Quote from: tony3d on September 27, 2013, 05:05:17 pmI thought it was an upper voltage limit you could set so that if, while connected to a circuit, some careless person comes along , or you have a blond moment, and accidently spins the adjust knob it would kill the output when it hits that limit to save frying your circuit.

author: tony3d
author_rank: Frequent Contributor
timestamp: September 29, 2013, 10:07:04 am
content: Quote from: Jonny on September 29, 2013, 08:56:43 amThat's exactly what I thought, but I can't seem to get it to do that. The over current seems to work correctly. You set it for the max current you want, then turn on the output, press the OCP button, and when you bring up the voltage, and the current rises above that set limit, it shuts down the output. Can't seem to figure out what their implementation for the OVP is though. Other than that, this supply is a real winner! For the money it's accurate, stable, and actually looks pretty nice.