Ask MetaFilter questions tagged with relay

Weird Wireless

lockedroomguy — Sun, 05 Jul 2009 09:48:42 -0800

Apple Airport WDS network with two devices: a Extreme base and a relay Express. My Powerbook connects ok. My PCs connect to the Extreme base fine. They can also SEE the Express relay, but they can't connect to it. I think the base and relay have identical configurations so I don't know why. I had a successful network with an Apple Express base station. I wanted to replace it with an Extreme, and then use the Express to extend the network. The Extreme would be downstairs where the Powerbook usually is; the Express upstairs where the PCs usually are.

So I configured the new Extreme by choosing the option of copying the settings from an existing base station--in this case the Express. The Express had WEP 128 security with a 13 character WEP passphrase that was converted to a 26 character hex string by the base station. So I assume the new Extreme does too, or maybe it's converted the WEP key to a WPA key--I can't tell. The point is that I did not enter any key when I set up the new Extreme--I just told it to get the settings from the old Express.

The new network worked fine, and all devices that could connect before can connect now. Note that this meant I was using the same key which I had been using before on all devices.

Then I wanted to set up the original Express to extend the new network. I reset it to factory defaults, then used the Airport Utility wizard to have it extend the new Extreme's network. I changed one setting on the Extreme here--I set it up to allow it to be used by extending devices.

So: Broadband cable connection comes into modem, Ethernet cable leaves modem and connects to Airport Extreme through WAN port. Extreme is broadcasting a wireless network with the name (SSID) HOUND, and the Express is plugged in remotely only to a power outlet, also set up with the name (SSID) HOUND.

When I browse for networks with my Powerbook, it sees a single network called HOUND and connects fine.

When I browse with Thinkpad, it sees 3 networks called HOUND. One has the MAC address of the Apple Extreme gateway, and has the weakest signal. One has the MAC address of the Apple Extreme SSID and has a medium strength signal. The 3rd has the MAC address of the Express. It is nearest to the Thinkpad, and has the strongest signal.

So I try to connect to the Express because it's closest, and the connection fails, every time. I try to connect to the Extreme, and the connection succeeds, every time. But they are supposed to have the exact same settings.

Same behavior on my second PC, an HP desktop with a Netgear card.

Both airports were broadcasting on the same channel (11), so I updated the Express to broadcast on 10. That didn't have any effect.
So my questions are threefold:

1) Should I see 3 wireless networks in the configuration I desire or do the 3 networks indicate a problem?

2) How do I either fix 1) or get my PCs to connect to the Express?

3) How do I know if my Powerbook is connecting to the Express or Extreme? (Because when I move further from the Extreme and closer to the Express I want it to use the stronger signal. How do I know if it is? Unlike the PC network browsing tool, the Powerbook only sees ONE network called HOUND.)

diy relay coil

sailormouth — Tue, 28 Oct 2008 17:22:37 -0800

DIY relay coil I want to make a few coils for some reed switches I have to make my own relays.

I am using relays to isolate two systems. My control/relay trigger signal is 5v up to 20mA, but the lower the mA the better. The signal I am switching is 5v low mA.Both systems are battery operated, but the control system/relays can be operated from 9v wall adapter, control sig is still 5v.

I have a spool of awg37 enamel covered magnet wire for the coil. I built a small rig to wind the coil. I am not sure how much resistance I need to make the relay operate efficiently without overheating the coil, another component, or quickly depleting the batteries. The duration of closing the switch is short, but the frequency of closing is often.

The glass body of the reed switch is 1.5" long and slips inside of a straw, which is what I am winding the coil onto. I am not sure if I should make the coil over more of the entire switch body (1.5") and thinner. Or shorter (0.5 - 1.0"), thicker, and centered over switch contacts.

So far I have made one coil, of the longer thinner style, which took 500 wraps to get 21 ohms. Purchased relays I've used before were 9v 500 and 1k ohm. So if I need that kind of resistance these would be huge.

Can you help with a resistance range to shoot for and style of winding (long/thin or short/thick)? I found info on pickups and voice coils on google.

Could someone tell my if my door is wide open?

doctorpiorno — Tue, 15 May 2007 02:12:12 -0800

I believe the mail server associated with my domain name is acting as an open relay. Hosting company claims everything's good. How can I double-check? I'm building a website to advertise my services as a freelance translator, and to that effect I recently bought a domain name and one year's worth of web hosting at a well-known hosting company. My website is not up yet, but I have now switched all my work-related e-mail to the address associated with my new domain name.

A few days ago, a couple of my clients reported that their spam filters had mistakenly filtered out some of my messages, which worried me enough that I decided to look into possible reasons. It was then that I discovered that the SMTP server provided by my hosting company is apparently accepting all incoming connections without even requesting an username and password. I'm no expert in e-mail protocols, but if I'm not mistaken that's what's commonly called an open relay, which I understand is a very bad thing.

I immediately contacted tech support at my hosting company about this. They insisted that everything is hunky-dory and referred me to this site, which says my mail servers seem to be closed to relaying. I'm not convinced, though: right now, using PopCorn (a lightweight e-mail client), I'm consistently able to send e-mail without an username or password and using whatever "From:" and "Reply-to:" address I care to give. Again, I'm not an expert, but this doesn't look right to me.

For the record, the SMTP server will take my username and password if I bother to give one - it just seems to send the e-mail just as well if I don't. If I try to login with SSL, Outlook does warn me that "The certificate's CN name doesn't match its passed value", but it behaves normally if I choose to ignore it.

Right now I'm quite concerned about my mail server being blacklisted, used to relay spam, used to spoof my e-mail address or any combination thereof. Could the networking experts in the Hive Mind confirm whether the symptoms I have described are indeed something to be concerned about?

If this is as worrying as I have so far assumed it is, what are my options apart from switching to a different hosting provider?

Thanks in advance everyone!

sexy baby and bad connection?

fidgets — Thu, 13 Jul 2006 10:51:00 -0800

can I turn a wireless router into a range extender/relay? Im interested in extending the range of my wireless network throughout my house and yard. Currently have an Apple Airport Extreme hardwired to the modem and I would like to use a second router (this to be specific) to boost the range downstairs. Would the second router have to be hardwired or could I just get it to pick up the wifi signal and extend it? If having two networks set up is the solution that wouldn't be the end of the world, but I'd like to not have cables running through the halls.

Care and Feeding of My 1950s Low Voltage Relay Lighting System

salsamander — Mon, 15 May 2006 18:02:45 -0800

1950s era Low Voltage Relay Lighting - My new home has a system, and I'm not sure what to do if it ever breaks. Are there any good resources for parts out there? Any good discussions on these systems? Books I should pick up?

Help me build a relay & timer electronics project please.

odinsdream — Sun, 14 May 2006 16:15:24 -0800

I'd like to trigger a relay that momentarily closes a switch based on the voltage of another wire. Maybe. I think. Please help me with this basic (I hope) electronics project. Volkswagens with a hatchback have a "safety" feature that requires the flip of a switch in the driver's door before the latch on the hatch will function. The doors must also be unlocked.

I'd like to automate this process by tapping in to the wire that signals whether the Unlock button on the remote has been pressed. When this wire signals that I've pressed the button, I'd like a relay to close the hatch switch momentarily. So, this would be the same thing as me physically unlocking the car, opening the door, and pulling the little switch.

It might be necessary to delay the relay with some kind of timer - thus the switch would be thrown a few seconds after the unlock button gets pressed.

I have this controller, which already listens to the Unlock wire to accomplish its function. I have access to +12V, if that's necessary.

How do I go about building such a device?