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View Full Version : cheaper modems than the CH1786A



justin weber
01-15-2006, 09:57 AM
I want to use a modem in a future BS2 application, but the dang Cermetek CH1786A costs $59 a piece. I am getting a quote by email from them any time now for 2 of them. It will probably be highly unreasonable. My question, help me out please, Is there an easy way to interface with a non-winmodem-PCI card? Or do we know of any modems with the cermetek chip on it that we can unsolder. I can get a pci modem for $9(I didn't check the winmodem status). You can get an externel V.92 modem with callerID support cheaper than that single modem chip. The cermetek with caller ID is CH1786-C and who knows how much more that is. Does anybody know if I can simply solder wires to a low profile PCI modem and get it to work. I can't imagine it being that complicated. Except that you probably would need strobe circuitry to allow the modem to communicate all the time, not just at interupts on the PCI bus. Then it should be as simple as connecting RX,TX and power. Am I wrong? let me know. I don't want to pay over $120 to get 2 stamps to communicate over the phone. No DTMF is not sufficient, I actually need a modem.

Bruce Bates
01-15-2006, 01:46 PM
Justin -

What is the minimum acceptable baud rate for this proposed new modem?

Regards,

Bruce Bates

PJ Allen
01-15-2006, 10:23 PM
There are scads of external modems available on ebay that you could use via RS232.· Some used, some new.

steve_b
01-15-2006, 10:41 PM
If you don't need a fast speed....just go to a flea market or a local HamFest.
Luckily my work had a bunch of old 2400 and 14400 USR modems sitting about, and I've been able to interface a stamp to them.

My only problem is in testing....I've only got one phoneline and a cell phone. So I can dial and receive calls with the stamp/modem....but haven't been able to set it up to transfer data!

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Steve

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

PJ Allen
01-15-2006, 10:53 PM
So, you call up a friend --·for all he knows it's going to be a social visit.· When you arrive you have a six-pack under one arm and a box with your STAMP, modem , &c. under the other.· "Hey, man -- can I use your phone for a couple minutes."· Problem solved.

steve_b
01-15-2006, 11:08 PM
haha....it's more like a proper case (24) of Canadian beer!

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Steve

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

Robert Kubichek
01-16-2006, 12:00 AM
steve_b said...
If you don't need a fast speed....just go to a flea market or a local HamFest.
Luckily my work had a bunch of old 2400 and 14400 USR modems sitting about, and I've been able to interface a stamp to them.

My only problem is in testing....I've only got one phoneline and a cell phone. So I can dial and receive calls with the stamp/modem....but haven't been able to set it up to transfer data!


Make your own telephone system with two modems on it, there is plenty of info on the net to whip up a power supply for one.
There are also black box modules that do the same thing....
If I remember its only 48vdc without the ring signal (90v ac on top of 48 dc power).


Bob N9LVU http://forums.parallax.com/images/smilies/scool.gif

justin weber
01-16-2006, 04:22 AM
I understand that the basic stamp has problems with faster modems speeds above, say, 9600baud. So any modem I get will automatically be set to 2400baud 8n1 as soon as I configure it on the computer. steve_b, do you still have these modems? We may be able to set something up where I could purchase at least one of the 1200baud modems. I have a 56k best tek v.92 modem I bought from newegg for $50 even. that is $9 dollars cheaper than the CH1786A without any type of shipping or postage or minimum order qtys. I opened it up last night and it was a single board and looked like it had space on the board to drill holes to mount above a BS2 controller board and use some type of plastic standoffs. That solves one side of my problem, now I need a second cheap modem. My dad works at agere and worked on a quad z80 modem, I recommeded making a alternative to the cermetek one chip modem but he said they don't do that anymore. Even so it would be sold in 1000 quanities probably. Anyway, thanks to so many for posting.

Robert Kubichek
01-16-2006, 04:40 AM
justin weber said...
I understand that the basic stamp has problems with faster modems speeds above, say, 9600baud. So any modem I get will automatically be set to 2400baud 8n1 as soon as I configure it on the computer. steve_b, do you still have these modems? We may be able to set something up where I could purchase at least one of the 1200baud modems. I have a 56k best tek v.92 modem I bought from newegg for $50 even. that is $9 dollars cheaper than the CH1786A without any type of shipping or postage or minimum order qtys. I opened it up last night and it was a single board and looked like it had space on the board to drill holes to mount above a BS2 controller board and use some type of plastic standoffs. That solves one side of my problem, now I need a second cheap modem. My dad works at agere and worked on a quad z80 modem, I recommeded making a alternative to the cermetek one chip modem but he said they don't do that anymore. Even so it would be sold in 1000 quanities probably. Anyway, thanks to so many for posting.


I have seen those multi modem boards using socketed modem chips on Ebay. You might find some on Ebay right now...

Bob N9LVU http://forums.parallax.com/images/smilies/scool.gif

justin weber
01-16-2006, 05:11 AM
oh sorry bob, that was just a tangent I went on the the post, I really need just a cheap 2400baud external modem. Don't want to buy a 56k modem because it would be a huge waste of money to downscale it to 2400baud anyway. I was really hoping someone would come up with a way to use a very cheap PCI modem with the stamp.

Robert Kubichek
01-16-2006, 05:30 AM
justin weber said...
oh sorry bob, that was just a tangent I went on the the post, I really need just a cheap 2400baud external modem. Don't want to buy a 56k modem because it would be a huge waste of money to downscale it to 2400baud anyway. I was really hoping someone would come up with a way to use a very cheap PCI modem with the stamp.


Ohh, okay. Then an external modem would be best, connected via a 232 level shifter...With PCI it would almost imposible to do it easily.

Bob N9LVU

Forrest
01-16-2006, 06:13 AM
I Googled emdebbed modem and found www.halted.com (http://www.halted.com) is selling new Rockwell 33.6K Socketmodems for $4.95 - search for P/N SFV336ACFSPH0D6A0P1

If you click the 'more details' tab in the middle of the page, there's a link to the Data Sheet for the Socketmodem

justin weber
01-16-2006, 07:27 AM
Well done Forest, I think you solved the puzzle. I found a Wintec embedded modem DIP40 (jameco p/n #487242), That is about $10 cheaper than the CH1786A. I am buying 4 of those socketmodems. Way smaller and easier(and cheaper) than gutting external modems and mounting the board with standoffs on the main project board. THANK YOU. Looks like 232 serial support is just as easy as the ch1786 and can be made removable using a IC socket.

steve_b
01-16-2006, 08:02 AM
I don't think there's much of a difference between a used 2400USR external and a used 56kUSR external. You'd get the 2400 one for $5 and the 56k one for $15 at a flea market!

Do you have any 'older' computer shops around? Heck, go in to a regular joe shmo one and see if they have any they'd be will to sell to get rid of!

I do still have my modems, but am not willing to part with them. I've plans for them down the line.

Also, you don't really need level shifters with them....well, I didn't. The stamps output TTL level rs232, which the modem seems to pick up just fine, but you DO need to remember to use the series resistors on your stamps rx lines (coming from the modems' Tx line) to limit the current so as not to kill a stamp pin.

As far as building my own telephone test system....I thought about it, but honestly didn't have the time to hassle with wondering if my 'make-shift' POTS was working or if it was something screwy on my modems/stamp....
I'll work it out eventually....I'll get the data jack/cable with my next cell purchase.

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Steve

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."