DROK DCDC Buck Converter, DC 5-40V to 1.2-36V Power Supply Step Down Voltage Regulator 36V 30V 24V 12V 5V 3.3V 8A 100W Adjustable Volt Reducer Module

I'll start this review by saying that I like this module. It seems very well constructed, and it is a wonder of Chinese manufacturing that it can be sold for this low price. Try pricing out the cost of the various components and heat sinks, and you'll see what I mean. On the other hand, along with the low price, there will be some infant mortality failures, so you may get the occasional "smoker".I purchased this converter as the front end regulator of a programmable bench power supply that I am building. I only need 3A maximum at 3V - 26V out of it, so I haven't tested it beyond those levels. I can say that the module hardly gets warm under these conditions. Good heat sinking and decent efficiency from the on-board switcher.However, there seems to be some missing information as to the actual specs of the module. One place says 30V maximum input voltage, and in another in the spec says 40V max. So which is it? For the record, I'm going to be powering it from a 24Vac transformer with a full-wave rectified voltage of about 32V, so it makes a difference to me.One reviewer thinks this uses a XL4012 buck converter, while another thinks it's an XL4015. You can't see any labels on the regulator package without desoldering several components, which I didn't want to do.So, to try to answer these questions, I did some testing. First, using a digital oscilloscope, I measured a switching frequency of about 180kHz, with some variation under load. (The peak-to-peak noise voltage under load was about 60mV.) I also measured an on-board reference voltage at the feedback pin of 1.25V. These results rule out the XL4012 which switches at 300kHz with an on-board reference of 0.8V. (As a side note, XLSemi no longer lists the XL4012 as a product - likely it's been obsoleted.)The XL4015 is still a candidate, however. It has the right switching frequency and reference voltage, but it's only rated for 5A continuous. However, on XLSemi's product page (http://www.xlsemi.com/product.html), they list the XL4016 which looks exactly like the spec for this DROK regulator.If you pull up the data sheet for the XL4016 (http://www.xlsemi.com/datasheet/XL4016%20datasheet.pdf), you see:1) It's rated for 40V input voltage (which makes me happy)2) it's rated for 8A continuous output (with proper heat sinking)3) it has a 180kHz switching frequency and 1.25V reference voltageI did some further measurements on the module itself. The spec on the XL4016 says that the minimum input voltage is 8V. However, when I set the output voltage to 3.0V and drove a 2ohm load (1.5 amp output), I was able to run the input voltage down to 4.05V before the regulator started dropping out. So it does work fine at lower voltages than the 8V in the XL4016 spec, but with somewhat increased dropout voltage.Lastly, I looked at the voltage setting resistors. The potentiometer is 50 kohm. The adjustable output voltage is set by the following equation: Vout = 1.25V *( R2/R1 + 1), where R2 is the setting of the pot, and R1 is a fixed 1.5kohm resistor (a small surface mount component located on the bottom of the board right across from the regulator feedback input pin). Of course this equation is true only if the input voltage exceeds Vout by at least the drop out voltage.Someone commented that they want to replace the potentiometer with a digital pot. I also plan to try that. But it's not as simple as just dropping in a digital pot. Almost the full output voltage appears across the pot R2, and very few digital pots will withstand more than 5V. So you will likely blow up the digipot if you drop one in. There are some digipots out there that can withstand higher voltages, but they are surface mount components. And I personally prefer to work with through-hole components, because I don't like having to design a printed circuit board when I'm trying out new circuits for a design. There is a way, however, to use the low voltage digital pots in this kind of application. More on that later, perhaps, if people are interested.Post Note: (3/15/15) I was able to replace the 50k potentiometer with a digital potentiometer (8 bit) and it works beautifully, giving 100mV step resolution in my application. To get around the 5V maximum voltage limitation of the digipot that I used, it required adding a few extra components - basically adding a secondary opamp feedback circuit. Pretty simple, and it is possible to increase the resolution further if needed.

I attached this at the bottom of my electric dirt bike to constantly power an 8 amp draw, It takes a beating at the bottom of my bike only attached with tie wraps and keeps functioning 100%. The wires are even held in place firmly by the screws and the voltage hasn't moved with all the jumps, bumpy off road riding etc.I needed to cover the top of it to prevent lots of dirt and water from spraying directly into the unit from my front tire, so I decided to thermal epoxy an extra heat sink I had laying around on top of the heat sinks already on the unit. I ordered artic alumina thermal adhesive to easily join them together.http://www.amazon.com/gp/product/B0009IQ1BU?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s00The unit will get hot without airflow at higher amps, like 8+, like if sitting out on a table without good airflow. It doesn't get hot or even warm at the bottom of my bike, probably because of the airflow and possibly the extra heat sink I added.If you plan on really pushing this thing at high amps then I would epoxy on an extra heat sink like recommended in the description. But of course test it out first and see how hot it gets to see what you will need.

At first the regulator worked like a dream. Needed to set the output voltage to 12 exact, and that's what I got. The input was 19A at 6.3A, so well within the 4.5-30V range. I had the regulator set, hooked the device up to my LED strips for a test run, and it worked for about 10 seconds before the lights dimmed and I started to smell a burning from the board. The heat sync was warm but not untouchable. Although, I did hear a crackling sound, as if there was some plastic burning somewhere. I unhooked my lights and took out the voltmeter. Tried adjusting the regulator again, but it was stuck at 6.0 volts (not amps) on the output. wouldn't move up or down no matter how I adjusted the screw.Seems as if quality control on these things is hit and miss at best. But that's what you get for buying cheap parts. Lesson learned. Never again.

Excellent product and probably the best we've had so far.Added a cooling fan and putting it to the test! So far readings are great. 14.2v input using 14 awg wire 6ft long + 1ft long -. Have device set at 5.12 volts and its peaked 14.28 amps and shut off, holds 8-9 amps perfectly. A while back I decided I wanted USB ports in my car to charge cell phones and children's electronics using USB (seems like everything is USB charged now, I like it!) And my husband did it a few months ago but had a hard time finding something that could power all those ports he installed through out the car, and he installed this little wonder as soon as it came out the mail box. And its awesome. This is the 3rd power source we've tried on it and this is it!The tests was done using a ammeter and digital multimeter, everything we could plug in on USB and using his E-cig pass through on medium-high. And peak test was done shorting it out (simulating what it'd do in the event of a short or overload) also found the safter features of the device responded faster than a 10 amp fuse. I guess that's a good thing. So your overload/short circuit shut off may be a bit differentExcellent product DROK, we'll be ordering many, many more. We own a performance/custom Automotive business and sure we'll start offering USB power now being we've found what works great!Thanks

Worked about 10 minutes.