Install SNMP (Simple Network Management Protocol) on Debian     I’m writing this tutorial to help other that may have the same problem I had. Let me explain to you: I have a Debian server called debian1 which has external ip 1.1.1.1 on eth0 and a local ip 192.168.1.1 on eth0:1, and a second Debian server called debian2 which only has 192.168.1.2 local ip on eth0. I need to access debian2 with ssh from the internet. I cant do that directly because debian2 does not have an external ip address to connect to the internet. But we can use a port forwarding rule on debian1 so that I can access debian2 trough debian1 on a specific port. The only command you have to use is:

iptables -A PREROUTING -t nat -p tcp -i eth0 –dport 88 -j DNAT –to 192.168.1.2:22

after entering this command debian1 will forward any request on port 88 from eth0 to 192.168.1.2 on port 22. Now all I have to do is to enter 1.1.1.1 port 88 in putty and I can log-in to debian2 trough ssh. That’s it short and simple about port forwarding.

October 27th, 2007

Serial port infrared receiver

serial-port-ir-receiver

This project is really easy to build, anyone can try it. After reading this tutorial anyone can build this. You just need the tools and the parts list and you can start building it. I first build this project about 2-3 years ago when I found the schematic on a website I don’t remember which website, and I gave it a try. Surprise, it worked! And it worked fine.

The receiver it’s very sensitive, you can send signals with a TV remote from 10 m away very easy. You don’t even need to point the remote at the receiver, it’s so sensitive it picks the signal that bounces from objects or walls. And if you think at the cost of this project parts list, it’s really cheap, about $4. You can build this on a board or just connect the parts between them.

There are various modes of assembly of this project: you can build the hole circuit inside the RS232 connector so only the IR sensor comes out, or you can build the circuit inside the connector and attach a wire with the sensor at the end. You can assemble it however you want. This is the schematic of the receiver, you can see that it uses an IR detector, a resistor, a diode, a capacitor and an rs232 serial connector. Very simple indeed.

serial-port-ir-receiver schematics

If you take a look at the ir detector code the last two digits represent the frequency at which the IR detector receives signals. I successfully used different frequency ir detectors and all of them worked with any remote I had around the house. If you encounter problems with some kind of remote you should try changing the IT detector with one of another frequency(it is optimal to use the 38 KHz receiver).

After building the receiver connect it to your com port and lets talk a bit about the software part. The receiver needs a software that is going to decode the signals and control various other programs that you want to control. As a software you can use a free software named Winlirc or Girder which you can buy for about 40 $(note Girder must be use together with a plugin that recognizes signals coming from our receiver, the plugin is named Igor and you can download it from link1 or from link2 there are 2 versions available , you should try the first one and if that doesn’t works the second one will work).

I’m going to teach you how to use the receiver with girder and Igor plugin because this is what I used. After installing Girder you have to install the Igor plugin , if you encounter any problems you can check the plugin’s website for answers or you can write a comment here and I will be happy to answer you. Now after you plug in the receiver start Girder.

Now you have to go to configuration to hardware plugins and check Igor SFH-56 device and set the correct com port.(click Link to see a picture explaining configuration of Igor plugin).Now your software is ready to receive signals from the receiver. Now the small green led in the lower right side of Girder should blink every time you press a button on your remote signaling the software is receiving signals. Now all you have to do is start configuring Girder to control various other programs by learning different keys and their action. Here are some pictures of assembled receivers:

serial-port-ir-receiverserial-port-ir-receiverserial-port-ir-receiverserial-port-ir-receiverserial-port-ir-receiver

serial-port-ir-receiver serial-port-ir-receiver

And here is the part list:

  • TSOP 1738 : ir receiver x1
  • resistor 3k3 x1
  • capacitor 100 nF x1
  • z diode 5v1 x1
  • rs232 conector x1




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