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Old 28th June 2012, 12:00 PM   #1
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Default DIY Cellphone?

Hello.

Just wondering if anyone know about any DIY cellphone kits for complete builds.

I used to work in a cellphone repair shop years ago, the circuits needed for making one should be easy to get hold of or work out, the PCB would be slightly tricky to get right. I am clueless about software.

I am also considering (dreaming about) buying a cheap "proper" cellphone, removing casing, batteries and so on, adding some cherry red mx switches for the dials, a voltage regulator and some good quality high capacity batteries, get some pro mechanical workshop to make a casing and buttons.

However sweet it sounds it would still be easier and preferable to get a complete kit.

I want standby and talk time! I want buttons! I want to be able to send my 50 sms pr year! I hate all touch screen phones! I want proper switches on the dials, no plastic crap!
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Old 28th June 2012, 12:17 PM   #2
DF96 is online now DF96  England
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Quote:
I used to work in a cellphone repair shop years ago, the circuits needed for making one should be easy to get hold of or work out, the PCB would be slightly tricky to get right. I am clueless about software.
Software is a major part of a cellphone. I assume you are an expert on microwave circuit and PCB design, and high speed logic? You have access to all the simulators you would need to validate your design? EMC and type approval, so you can legally connect to a network?
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Old 28th June 2012, 01:37 PM   #3
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There are minimalistic cellphones on the market
Giant Button Cell Phone for Seniors (and Simpletons)
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Old 28th June 2012, 02:15 PM   #4
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Quote:
Originally Posted by DF96 View Post
Software is a major part of a cellphone. I assume you are an expert on microwave circuit and PCB design, and high speed logic? You have access to all the simulators you would need to validate your design? EMC and type approval, so you can legally connect to a network?
SW is definitely not my strong side, not in simulation or in regards to programming, so to be fair to myself the only realistic way is to modify an existing design. Which would also save me from approval.

The most reliable designs I have seen did not follow the strictest rules of circuit design, but relied on simple but rugged construction. Correct screening, baking techniques with slightly too high temperatures and a bit too much flux have way bigger impact on the end result than most other things. Some of the best reliable designs combine above mentioned with a thorough rinse then gluing of ic's.

The best "proper" cellphones where in the days of the outboard antenna, you do not need many circuits in a cellphone, it is rather choosing the right ones for the job, and placing them with proper distance and screening in relation to each other. Most modern phones revolve around exterior design rather than the design of the device itself, sacrificing reliability and build quality for sales arguments and functions that make the phone slow and cumbersome, the older phones are way faster when it comes to calls and text messaging.

The days before the color screen was the golden era of "mobile" as I see it, slim small devices with excellent coverage and week long standby time with moderate use.

Kjeldsen:
Yes, that is close to what I have in mind for modification.

Edit2:
SAMSUNG Xcover B2710 seems interesting only with more battery capacity, real switches for the dials and a proper antenna

Last edited by KaffiMann; 28th June 2012 at 02:30 PM.
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Old 28th June 2012, 03:17 PM   #5
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Bump not intended.

I think I will buy the SAMSUNG Xcover B2710, battery capacity is good, it seems like a rugged well thought out design. If i need more battery capacity i can make a charger pack. Quad band is important, GPS is handy sometimes if I forget to memorize the local map (although I prefer being lost for a few hours).

Sorry about the rant, phone ordered, expecting it in a few days.
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Old 29th June 2012, 12:46 PM   #6
marce is offline marce  United Kingdom
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FCC and CE certification and testing...
I would strongly reccomend that you neither try to make your own or mod an existing design, this is not the sort of electronics that DIYers can do, the EMC implications are immense. Its hard enough to design these things when you have all the resources behind you...
As to designing boards for these sort of devices you need a bit more than eagle, a full proffesional PCB system prefferably with a SIV (signal integrity verification) add on package is a must, and a few years of PCB layout experience doing such complex designs (again the PCB requirements are a bit beyond DIY layout). Shielding, done a lot of PCB based RF shielding, if not you will require expert advice and prefferably some way of testing it.
If it is not done right all you will do is transmit noise everywhere, at the least it will upset the rest of your circuitry making it unreliable, worse you will transmit noise to a wider audience, which could lead to fines and other consequences.
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Old 29th June 2012, 01:33 PM   #7
DF96 is online now DF96  England
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The thread reminds me of the time my sister seemed puzzled when she learnt that the actual cost of a mobile phone was hundreds of pounds (this was a few years ago) but they are heavily subsidised by the networks so we pay much less. "How can it cost so much; it's just a phone?" I reminded her that as well as a phone, it also contained a powerful computer and a sophisticated radio transceiver - all in a tiny package you can pop into your pocket. "Why has it got a radio in it?" I asked her to think about where the wires would go, if she used a phone in the middle of the street. My sister is not stupid, just clueless about technology.

I know I couldn't design or build a mobile phone but I only have a PhD in EE (and an MSc in telecommunications) and, unlike the OP, have never worked in a phone repair shop.
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Old 29th June 2012, 01:42 PM   #8
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Why not simply buy a GSM modem (with audio) and control it with a microcontroller and the user interface of your choice?

One mounted in a box needing just 12V and RS232 to control it costs about 5 from eBay. Or there are tiny PCB modules available pretty cheaply from Farnell and other suppliers.
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Old 29th June 2012, 03:50 PM   #9
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Why bother? 2 years ago, in London, we had to buy new phones (ours did not work, allthough so promissed by the local service provider). Cost per phone 3.95 BP + sim card. E
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Old 1st July 2012, 04:19 AM   #10
dangus is offline dangus  Canada
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Build something that controls a phone using Bluetooth. Or, there are phone modules available; Sparkfun used one to turn an old school dial telephone into a cellphone.
Port-O-Rotary You can buy a finished rotary dial cellphone for $300, although I think that's an inconvenient form factor for a portable phone, unless you keep it in a briefcase.

The lazy way to do it is just get a Bluetooth cell phone gateway that lets a wired phone (with or without landline connected) receive calls from a cellphone. Rotary phones probably won't be able to dial out unless you get a separate touchtone generator, or a gizmo that turns pulse dialing into DTMF ($20 and up).
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