New wireless router

-
After five years of trouble-free operation with my 11Mbps D-link DWL1000-AP 802.11b wireless access point I decided to upgrade my home wireless gear. The USRobotics USR-8000A router with print server and the access point were replaced by an SMC2804WBRP-G that contains a print server (for USB printers), 54Mbps 802.11g wireless access point, four ports FastEthernet switch and router, all in one nice box.

My initial research on the net told me the product firmware was quite poor, with lots of users reporting different problems. However, because the retail price was under 100 Euros I decided to give it a try.

The results: I configured the router off-line and then I just switched the old by the new gear on the fly. The p2p software I was running on a server continued running as happy as before. I was a bit dissapointed as the unit's current firmware does not provide fixed IP mapping, this can be a problem.

After some hours of happy networking my son complained an streamed show he was watching was choppy and he was getting some network cable disconnected warnings. A closer inspection revealed the router was reseting itself sometimes. Not a good thing. The problem stopped when I disabled packet inspection features.

My opinion is that this is cheap wireless router with a nice look and decent performance but lacking on the QA side. It has some interesting features and lacks of others. I give it just a C grade.

One detail: the printer server is an LPR server, but the printer queue name is not lp but LPT1. Armed with this info my unit allows me to print from Windows, OSX and Linux like a charm.

Comments

Post a Comment

Popular posts from this blog

VFD control with Arduino using RS485 link

-
Image
Variable Frequency Drives ( VFD ) allow the control of spindles so speed can accurately be controlled and a detailed acceleration profile for the spindle and reverse rotation can all be handled. In essence a VFD is an three phase inverter for three-phase AC motor. I am using a popular (I mean cheap) Chinese VFD and though the reference manual is not great, I could see there is a built-in RS-485 port. I usually control the start, stop and speed selection using the keyboard on the unit but I thought it will be more useful if I could control everything from the same Arduino is doing our CNC table control. Some cheap RS-485 off eBay and some lines of code later, I can start, stop and change the speed from an Arduino. What a cool thing to have! Some configuration of your VFD are needed before you can use it like that.  You need to set PD163=1 (I am using address 1 in the code). PD=164=1 (for setting serial to 9600bps) and PD165=0 (for using ASCII and 8N1 character format)
Read more

How to get sinusoidal s-curve for a stepper motor

-
Image
After some experimentation, and delving a bit into the math of motion, I realized there can be a significant difference on the motion of a machine by just making small changes. A common and popular approach to smooth one axis of motion is to use a trapezoidal speed pattern, where acceleration and deceleration are uniformly accelerated movements (aka constant acceleration motion) separated by a portion happening at cruising speed. The problem comes with the fact that, while that approach is simple to understand and to code, it does contain sudden changes in the acceleration, that show as spikes on the acceleration derivative, called jerk. These sudden changes in the acceleration translate into undesired vibration in our machines. Most of that can be eliminated by selecting a motion pattern that does not contain sudden changes of acceleration. If we chose a mathematical function for our speed whose second derivative is continuous, then we reduce system vibration quite a lot. One ma
Read more

Stepper motor step signal timing calculation

-
Image
While we use stepper motors in many devices, the timing of the step signals is not always well understood. Most of us can see how a fixed speed is a bad idea unless the speed of motion is really slow, but it is fixed speed what is really to generate with simple code. You just can use the Arduino Blink example to send a fixed frequency of pulses to a stepper motor driver. If too slow, just reduce the delay value. But for most real-life applications variable speed controls will perform better. These systems will speed up the motor to a given maximum speed and it will slow it down to stop at the desired step count. But understanding the math behind this process is sometimes not obvious. Let us start with the simple case of the so-called trapezoidal speed motion profile. Here motion takes place in three phases: acceleration, constant speed (cruising) and deceleration. But the point is how can our code create such a behavior. Stepper motor drivers usually accept two signals to control
Read more