On this page I will occasionally post a review of hardware I’ve attempted to use in some fashion. In many cases this is in a project where I had to control the hardware via software. In other cases it might be a stand-alone piece of test equipment. But in any case I will try to provide an objective review based on my direct experience.
Product: EZServo, Model EZSV10
In their print ads AllMotion claims that their products are as simple as “child’s play” to use. My experience with the EZServo controller doesn’t support this claim.
First off, the documentation provided with the controller is sub-par. It is poorly written, does not completely document the behavior of the controller, and provides only a few examples.
I also discovered that little things like using mechanical switches as limits wasn’t supported in the revision of the firmware I was using (2.81). The documentation seems to imply that this is possible, but does not come out and explicitly state what can, or cannot, be used as limit inputs. It is only implied on the wiring diagram provided, where the opto-isolator inputs are shown as limits, but the switches are not.
There are also some response latencies that are not documented anywhere, so trial and error was used to determine when to check the device for a valid response (it varies between about 100 mS and 500 mS).
Based on my experiences, and on those of another engineer dealing with the AllMotion products, I can’t say as I would recommend them. I think that they could perhaps redeem themselves by providing documentation that doesn’t come across as something written by someone who didn’t like writing (or who didn’t know how), and perhaps some additional testing of their products might uncover the little gotchas in-house rather than letting their customers discover them. As a colleague of mine put it: “It’s a good idea, but rather lacking in the execution.”
Product: GPIB-USB Controller
This is a very handy little device that allows one to communicate with
GPIB/IEEE-488 interfaces on test equipment using a USB port. So far I’ve
used it with an old HP-1631D and it works great. At $149 it’s a good deal,
The interface doesn’t come with any fancy software, it’s just an interface.
The website provides links to sources for USB drivers and GPIB utilities.
Gettings things up and running wasn’t exactly plug-and-play, but it wasn’t
that hard, either. After some reading and a bit of fiddling I was able to
dump a screen from my logic analyzer, capture it, and drop it into a Word
When combined with John Miles’ GPIB Toolkit (free) and the GPIB print
capture utility from PrintCapture.com ($97) you have a complete, low-cost
GPIB control and data acquisition system. Note that John Miles’ GPIB Toolkit
(see below) does not include a tool to grab PCL data dumps–it only handles
graphical output (like that generated by an oscilloscope or spectrum analyzer).
The PrintCapture tool (see below) is necessary to capture output in PCL form
that some instruments generate (like the 1631D). My total time investment
from when I unpacked the hardware to being able to create a Word document
with a nice image was about an hour.
All in all, I would recommend this to anyone who doesn’t want or need to
spend a lot on special purpose PCI cards for GPIB I/O.
Prologic also sells a GPIB-Ethernet interface as well, but I’ve not had a
chance to work with that product.
The Prologix website is here:
You can find out more about the GPIB Tools here:
PrintCapture can be ordered online from the company’s web site:
Product: K8061 Extended USB Interface Board
The K8061 is a low-cost I/O board kit that provides both discrete digital and analog inputs and outputs. There 8 digital inputs, 8 digital outputs, 8 analog inputs (10-bit resolution) and 8 analog outputs (8-bit resolution). It retails for around $110.
This is a kit, so assembly is required. The board layout is clean and well organized, but I had an issue with the fact that it is single-sided. This means that getting the solder to flow and form well-shaped fillets can be a problem. It would be a good idea to clean the board with alchohol beforehand to make sure the solder will flow. I think Velleman could have spent a little bit more and made a double-sided board with plated thru-holes. I would have paid the extra for that. I also found that it is a good idea to have a little tin of solder flux paste handy, since some of the connections are stubborn no matter how clean they are.
Performance-wise this unit does everything that Velleman claims it will do. It is not fast, however, so don’t expect to be able to coerce it into being a digital oscilloscope or logic analyzer. But if the application involves low-speed events (lighting control, security system, electronics burn-in monitor, radio transmitter control, etc.) then this is an excellent alternative to high-price data acquisition equipment.
My biggest gripe, however, doesn’t involve the PCB, but the software. Although the instructions does include schematics, the source code for the two PIC processors used in the design is not included, and from what I’ve gathered Velleman has no intention of letting it out. You do get a DLL that can be linked in with a C or C++ application, and it can be “wrapped” for use with Python. But, again, no source code. This is unfortunate, since this is a board that is ripe for experimenting. Nonetheless, for $110 it’s still a good deal, just don’t use it in an application where you have to have a high level of reliability, because there is no way to look inside and see how well, or how badly, the firmware and interface DLL code was written.