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Author Topic: DC-DC back converter getting smarter, here is the NEW ZK-J5X 5A ( Mini Review )  (Read 1288 times)

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Online Kiriakos GR

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It looks like that youth of China (electronics developers) makes noticeable steps forwards developing automation this helping low cost buck converter chips to deliver much more usability.

ZK-J5X circuit this is fresh technology of 2018, it is an alternative product design which aims mobility in to the application of constant current charger and constant voltage simple battery charger.
At my Black Friday Day I did spent 5.80 Euro so to order one unit for testing at ITTSB Blog.

Introduction:
ZK-J5X electronics circuit this arrives with Plexiglas top and bottom plates, the idea is this circuit to serve primarily hobbyists them requiring constant current charger with on-board voltmeter and ammeter, among with easily adjustable volts output.
 
Software which is in control of ZK-J5X it can handle bellow functions.

Voltage adjustment  +/_  (in micro-steps or fast mode)

Default start-up mode ( On power-on if output will be OFF or ON)

Voltmeter & Ammeter In/Out reading selection.

Ammeter review of Amps or Watt  Supplied text document does not deliver clear How-To description?
 
Current limiter this is manual adjusting pot, and charge complete indication Led this has preset of activation at 5% of Max set value.
For example at 2A setting when current go less than 100mA then (Charge OFF Led this activates).

My first though was that this module it can become a permanent charger for my battery pack of 14 NiCD this be power source of my 10V voltage reference chip.
I also thought that ZK-J5X it can read output voltage even by not be powered with input voltage.
Even by reading all available operating instructions, I do not feel confident that this programmable DC-DC back converter it is the best choice for my own application.

This is why I did also order and one PCB of basic LM2596 DC-DC Step-down Adjustable CC/CV with three adjustable pots and 2018 new PCB.
One pot for CV ADJ, second pot CC ADJ, third pot for minimum current ADJ ( Charge complete LED activation).
Fresh made PCB also includes holes for external three pin (Green / Red ) Led !

ZK-J5X product overview:  My own thoughts
This very small item it can offer some good use even to experts, this combined with AC voltage transformer with diode bridge up to 30DCV unregulated output and therefore this becomes an independent small charger.
My very expensive and powerful bench-top power supply, this include CC & CV but it has single output, keeping this busy for battery charge this is a terrible idea.

My second PSU this DIY made, bench-top power supply with LM317, I do have voltage range of 1V~24V with 1.5A max output but no constant current limiter,  mainly this is my alternative source for cooling fans testing and circuits with known consumption.

Therefore there is room in my lab for a ZK-J5X this inducing it own DC power source.
Very recently I did trash one old Panasonic Fax machine, I did kept internal pulsing power supply this is MITSUMI ELEC. CO. LTD SRF1382EK.
According electronic part specifications 24V output this can deliver 5A max, therefore this is best choice to get married with ZK-J5X  :)     

ZK-J5X this inducing it own heatsink but this is actually cooling down PCB it self, default ZK-J5X KIT  (PCB and housing) this will help this device to handle no more than 50W of power and  75W this is possible with active cooling.


For now I will deliver few stock pictures, and in a few weeks time which I will have receive my product sample, I will deliver more detailed information's.  ;)
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Online Kiriakos GR

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Now lets see electrical specifications of this Circuit.

Input voltage: 6.5-36V (If input voltage is lower than 6.5V, current meter reading is not accurate, LCD display below 5.5V is not functioning as expected)

Output voltage: 1.2-32V, factory default output 5V at every fresh start up..

Output current: It can work stably at 3.5A for a long time, and can reach up to 4.5A with (active cooling ) (adjustable current limit is about 4.2-4.5A)
 
Output power: According to heat dissipation this is 50W (within 3.5A), with active cooling 75W.

Voltage display: resolution 0.05V, range 1.2-32V, accuracy ± 0.1V
Current display: resolution 0.005A, range 0-4.5A, accuracy ±0.05A
Testing of such specifications this is a job for U1272A or DT4282, budget meters excluded. 

Conversion efficiency: about 94%
Working current: about 30mA

Input reverse connection protection: Yes
Output anti-backflow: No
Short circuit protection: Yes

At every start up (power on) it is required setting first output voltage due push buttons (default output this is always 5V Preset programed by the factory.
When required voltage output this is selected ( 4.2V for lithium, 1.6V for NiCD, or 14.4V for 12V car battery, then you do connect charging leads on the battery.
To minimize risk of battery discharge when input power gets off, you need to add a diode in the output positive pole.


Dimensions: length * width * height 70.5 * 48.4 * 28mm
Weight: 62g   
Plexiglas top&low plates must be assembled by the user.


Buttons usage:
1) In/Out short press ( selects In/Out Voltage & current source ) .. Long press activates Watt measurement ( Watt = VA if this is mAh this I will explore as soon ITTSB will test it.).

2) ON/OFF button control output ON or OFF, long Press set the default output state of the next power-on to be ON or OFF.

3) Up/Down buttons short press does micro-step adjustment, long press makes larger voltage adjustments.   

ADJ-I current adjustment potentiometer
Firstly rotate the ADJ-I current adjustment potentiometer counterclockwise, then use the multimeter 10A input to measure the output short-circuit current (directly connect the two test leads to the output terminal), adjust the ADJ-I constant current potentiometer clockwise.

Beware to avoid burning your DMM Fuse   I am assuming that counterclockwise this translates to minimum current setting which will increase as required, 3.5A output peak spike (inrush current) this is higher than 10A and it could burn you HRC fuse.
Therefore never retest output current when prior selected setting this is higher than 3A,  always start from scratch by setting the potentiometer at minimum output and then increase as needed.

Here I think that our product developer does not trust much his own current meter, and it does that because measuring refresh update this is very low, once per second or lower than that.  

ITTSB Blog this is armed with best multimeter & Oscilloscopes of our times,  ZK-J5X true analysis of electrical behavior this will be a walk in the park. ;)
For now bookmark this topic and visit us again at 20 of December. 
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Online Kiriakos GR

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This is an update,  I have bad news and more bad news to share  ;D

My package were lost and never arrived, and now I am not planing to re-order such a PCB.
But I am going to leave all above information's as Help for anyone who needs it. 
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Online Kiriakos GR

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132 Days for delivery ?  from Solomon Islands ?  (This is a small planet next to moon  :P )

Either way, this project gets back on track and I am planing to use a fancy case and power supply.  ;)
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Online Kiriakos GR

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Quick testing has started and here are my findings.

1)   Long button press this is 4 seconds.
2)   This PCB it should stay powered about 10 minutes, and then you may trust the display readings.
3)   Input voltage measurement contain error of  minus 100mV than real
4)   Output voltage measurement contain error of  minus 130mV than real 
5)   The circuit does not reset last voltage setting used after power off.
6)   For charge current less than 600mA, additional heatsink this is not required.
7)   Ammeters circuit this it more accurate.
8 )   Voltage scaling Up-Down this is in steps of 57mV?  This is terrible because there is no chance for you to set a precise voltage output, for example 4.10 V this is 4.190V multimeter reading (U1272A), and this is voltmeter measurement error with combined scaling error due buttons adjustment, which possibly original thought was to be at 50mV steps.

9)   When output is connected to battery, battery voltage above 7 V this is able to keep V/A meter active, and voltage measurement this is possible ( with included error) when input voltage this is disconnected.
This PCB will use approximately 10mA by been powered from the side of the load. 

Generally speaking, with unknown voltage calibration procedure, there is no chance about you correcting voltage measurement error.
Therefore if you think this PCB as Lithium battery charger, then this is not the best for a single cell.
But when there is chain of cells, these 75~190 mV difference from original panel setting, they can be easily seen as not noticeable. 

Additionally because of high switching noise at output, no one should think of it as power supply replacement.
This is a battery charger and this is what it should be used at, a battery cell does not care of high switching noise at 150 kHz.

From the other hand we should never forget that it is a major challenge about getting accurate voltage reading from a dirty DC power source, especially with a low cost VA meter.   
Therefore we should always evaluate carefully all plus and minus before a decision is made. ;)
 
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Online Kiriakos GR

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No matter how fancy it looks all this adjusting circuit and LCD (screen), actual delivery of power this is defined at XL4015 datasheet.
Actual handling wattage this is related to input voltage and load.
XL4015 Efficiency VS Output current this is tricky, this was tested with input voltage of 8, 12, 24 and 36V by it product designer. 

Now my own PSU source at final testing this shown as very generous delivering 118,8VA at Max ADJ output that is 26,40 VDC at 4,5A.

My ZK-J5X this has active cooling, a fan gets 5VDC and spinning gently by sucking air in the box (Crystal Jar).
It is interesting that ZK-J5X does not steal any input voltage at max setting, neither few millivolts.

It is also interesting that 4.5A limiting by the chip this is stable at all output voltages, I did tests at 1,2V – 4,2 – 14,4 and at max 26,40.

So, here it is, this is another unique design regarding assembly an Crystal-Jar Battery charger, this close enough to handle (charge) even 2x car / motorcycle or UPS battery cells.

Now in real life, its one battery cell this comes with charging specifications’ (written instructions - limits).
While I do feel confidence that this setup will not face overheat issues, in order to avoid overload and stress of this good in quality pulsing power supply (Japan), I will never force it this delivering higher current than 3A (PSU max specification this is 5A). 

Enjoy the pictures !!  8)
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Online Kiriakos GR

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I am adding here an interesting screen shot.  :)

This is the AC component when charging a Lithium battery at 4.2V  0,8A 

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