Simon Says – RND Lab DC Power Supply RND 320-KA3305P


Don’t try this at home, kiddies! Hi, in this
episode we’re going to look at the RND Lab 3 channel variable power supply. RND Lab is
in fact Distrelec’s own brand, so I have to admit the one thing that attracted me to this
particular supply was the price. It’s about 200 Euros give or take for a 3 channel variable
power supply that’s also digitally programmable. And that’s a pretty good price. The advantage
of a 3 channel power supply is, if your doing the type of work that I like to do like to
do with micro controllers and CPLDs and FPGAs for example, you typically want 1.8 volts,
3.3 volts and 5 volts for your device under test. And again for other types of electronics
you may want 5 volts, 9 volts and 12 volts. So the ability to get all of that from a single
lab power supply is kind of attractive. The nice thing about this is, you have 2 completely
variable channels, so you have 2 channels that can supply between 0 and 30 volts, 0
to 5 amps, constant voltage or constant current, and then you have a fixed channel which is
5 volts with 3 amps. So you can get everything that you need from this single supply. The
other thing is that you have 2 options to control it. You can either use the actual
control panel on the device and the display to set the different power outputs or amperage
outputs that you want, or it also has a USB and a serial input on the back. So you can
connect it to your PC and control it remotely. So if you want to do automated testing for
example or you want to have several presets that you just recall from the computer you
can use this device too and completely remote control it. So we’re going to do 2 things
in this episode. First I’m going to do the usual thing that I do, power it up, take a
look at the controls, take a look at the display and see if it’s any good.
But because it’s such a sort of, well I hesitate to use the expression ‘cheap’, but at 200
Euros it’s pretty much a bargain for this type of thing. One thing that I’m really curios
about is the build quality of it. I wanna know, for a lab power supply is it well built,
are the cables inside good, are the boards loose, is the soldering good, that
sort of thing. So what we’re actually going to do as the second stage is, we are going
to pull this thing apart and have a quick look inside and have a look at the build quality
of it and see wether it really is the value for money that it seems. The first thing you
notice about this unit is the pressed steel case, it’s a good solid construction. The
other nice thing about this is that I’ve seen some cheaper power supplies that actually
have ventilation holes in the top of the supply and that’s a really bad idea on a power supply.
When you’re having an electronics desk and you’re cutting wires and all those types of
things, you have small metal particles flying around all over the place and you don’t want
them falling into your power supply. This unit is side vented, which is a much better
idea, so they’ve obviously got that right. The other thing that you immediately notice
is the nice big display panel on it. If we power up the unit you can see that it’s an
LED panel, which is nice and if you’ve watched any of my other videos you’ll see that I have
a bit of a passion for big clear displays. I wanna be able to easily see what’s going
on. And this is really nice. It’s an LED display, so it’s nice and bright even if you have it
in a fairly dimly lit area. You can see quite clearly the channel 1 and the channel 2 output,
the voltage and the amperage settings that is in constant voltage mode and you can also
see the memory preset that you currently have set. One of the nice things about this particular
power supply, which a lot of cheaper power supplies don’t have is it has an independent control
here so you can actually set the device up and then turn on and off the power to your
device under test. The reason why that’s important is that on cheaper power supplies your only
real option is to turn it on or off using the power switch. The problem with that is,
when you power on one of these devices, the electronics in the device are unstable as
they power up. And that can cause a spike to come out of the actual power output to
your device. So if you’ve got it set up for 3 volts and it’s a sensitive device, hitting
this power switch could give you multiple more volts than you expect and actually destroy
the device under test. So the good thing about this is that you can power it up, let the
unit stabilise, you can set the power to how you want it and then you can turn on the power
to your device under test when you require it. And the idea of course is that powering
it on or off using this control will cause no spiking in the power output. We’ll connect
this up to an oscilloscope in a moment and have a quick look to see wether that’s true
and wether you get a nice clean power output from the device when you turn it on or off
that way. So to begin with let’s power up this power supply in the wrong way. I’ve set
it to immediately output 5 volts as soon as it’s turned on. So now we’ll just hit the
power switch and you can see that there’s a little peak there, it’s about 5.41 volts.
Actually that’s surprisingly good, the nominal output should be around about 5 volts. I’ve
seen power supplies do much much worse than that outputting many more volts than they
should do when you turn them on. And again let’s turn it off and there you can see a
little bit more of a peak there, 5.7 volts round abouts. So that’s the reason why when
you’re using these types of power supplies you should always make sure that you have
that on/off switch on the panel to be able to control the device under test. What we’ll
do now is we’ll just power it up and shut the power off and let the oscilloscope stabilise
again so we can see the measurement. So now the device, the power supply itself is powered
up, but the output to the device under test is off. And you can see that that’s outputting
no voltage at all. And then what we can do is turn it on, and you can see that the peak
that you get there is much smaller. And again turning it off: nice even drop. This is the
reason why you wanna have a power supply that has this type of control, because when you’re
turning on and off your device under test you really don’t want big peaks coming through
that can damage the thing that you’re testing. This power supply actually performs very very well. Here with the right way of doing it, pressing this button to get it on and off the peaking is absolutely
minimal. And even when actually turning it on and off from the mains it was surprisingly
stable. So let’s pull it apart and have a quick look inside. Don’t try this at home,
kiddies! So, there’s a couple of things that you can immediately see, when you pull this device apart. One is the steel frame itself continues inside the device, this is nice and solid. There is no way that that’s actually going to bend or flex when the device is in
use. The other thing is that the circuit boards are very well attached to this device, they’re
not moving around. You can also see the way the air flow in this is supposed to work as
well. You actually have a forced air flow with a fan, so the air is being drawn into
the side of the unit. And then these are all the bridge rectifiers that are going to be
controlling the power output and the air is going to be pulled across the transformer,
through the fan and then vented out the back of the unit. That’s a good design, it’s a
good forced air flow design where there’s no top ventilation required, everything is
coming from the side here. There is a nice fan in the back that looks like a 80 mm fan
on a big aluminium heat sink. So that’s going to be very effective at drawing the heat through
the system. And that’s important, especially when you got a ginormous transformer like
this in the middle supplying all of that current. The other really important thing that you
can see here is the smaller signals if you like, the lower power side of the device the
lower side is separated completely from the higher side of the device. In a lot of the
cheaper power supplies what you often see is that they bundle the connections together
so you actually have these mains cables handling the 240 volts zip tied to the low power and
the signals connections and that’s really bad. So on this one it’s really nice to see
that not only is it neat and tidy, but also the 2 sides are completely separate. And you
can see here that everything is actually on plugs as well, so they haven’t soldered the
wires directly to the PCBs. And that’s a nice touch, I mean it’s not strictly necessary,
but it’s good that they’ve done it. And you can also see that there’s glue around every
single one of these and the glue around these large capacitors here as well. So as the device
is being moved around, as it’s being transported all the way from China or where ever they
make these, it’s not going to be vibrating and things aren’t going to be breaking off
and falling loose because of that. So if we just turn the device around quickly to see
the other side of it, you can see a little bit more about the construction here. The
actual control signals are coming in this ribbon cable here, so there’s no control signals
coming through the bundle with these different power connections. Everything has nice little
aluminium heat sinks on it. It’s actually surprisingly well made. Quite often with these
types of devices the manufacturer can be… it can be a little bit low quality to say
the least. But actually this is surprisingly good. And up here you can see the RS-232 and
the serial board etc. And then that’s connected into the main board which then transfers it
over to the control board in the front here. So overall it’s quite an impressive build,
it has been well thought out, there’s plenty of air in there to keep the air flowing around
correctly, everything seems to be bolted down correctly, there’s spring washers on all the
places where there should be spring washers, the boards are all held in place with multi
points, there’s 1, 2, 3, 4, 5, 6 screws holding the main power supply board in. And everything
is nicely made, I mean these power cables are nice and thick, they’re obviously designed
to handle the type of power that’s going to be flowing through this type of device. So
overall it’s quite surprisingly good actually, you would expect for 200 Euros that this unit
costs a bit of a compromise in there, but I don’t see anything myself. It looks well
made, it’s properly bolted together, the quality of the components in there, and the build
quality of the PCBs, it looks really really good. So there you have it, that’s the RND
Lab 320 KA 3305P 3 channel digitally programmable power supply from Distrelec. I have to say,
I’m really impressed with this device, surprisingly so. I like the display, I like the way the
panel is laid out, nice big, clear displays, but also now having taken the top off and
having a look inside, I like the steel frame, the fact that everything is nicely and sturdily mounted inside there, the good PVC cabling, the separation of the high and the low side of the power supply is really good. The fact that you
can control it from your PC over both serial and USB is a really nice feature. So for 200
Euros there abouts, it’s really good value for money.

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3 thoughts on “Simon Says – RND Lab DC Power Supply RND 320-KA3305P”

  1. jasonbay13 says:

    i have the korad and blew out the switching transistors for ch1 and had replaced them and they had been working fine for months but decided to go out again and send a high voltage out of the output, i forget the voltage but i have a video on my channel with the problem as it happened the first time.

    really nice supply until you kill it :/

  2. Wojciech Majstrzyk says:

    For it looks like the test is done in a bit incorrect way. These are my thoughts:
    1. Supply is bad or output on/off Is improperly implemented. Even when you power it off with output ON, it should have output OFF every time you power it ON. No matter the previous state.
    2. Why you don't use single sequence and half the output voltage trigger to show the output on. Oscilloscope (even keysight) won't catch <1ms spike in 500ms time/div. You should set the trigger, single sequence, and time base to view just the small part of power on sequencing.
    See how Dave from @eevblog does it.

  3. Sebastian Kobyłka says:

    Hey. The power supply has 2 outputs 30v 5A. How to get 30V 10A? Is it possible to set on the power supply so that the output has a regulation range of 30V 10A?

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