Mail Archives: geda-user/2015/07/21/16:27:48

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From: Kai-Martin Knaak <knaak AT iqo DOT uni-hannover DOT de>
Subject: Re: [geda-user] [OT] I need help with selecting components
Date: Tue, 21 Jul 2015 22:27:19 +0200
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Spacefalcon the Outlaw wrote:

Hi Spacefalcon. Nice to see you on this list. I got to know you from
the openmoko mailing list. I agree with much of your diagnosis why
openmoko was so underhelming. Would put in a less radical way, though.
I hope your dumb phone project advances. If it actually delivers, I 
may be interested in a copy.

> some recommendations as to what parts I can use

I am based in Germany so my choice of distributors may not be viable
to you. The parts should be available worldwide, anyway.

> 1. A pushbutton switch for power-on and reset buttons.

I'd use one of the "microswitches" wich come in various heights. Any
of these at TME would do:

The four pin version is fairly generic. Compatible switches are sold
by many manufacturers. When in doubt, I go for the most cost effficient.
I tend to have a bunch of these in the drawer:

My geda footprint for this button:

My corresponding symbol with the footprint preselected:

> I am building
>    a board based on a cellphone chipset, and the power management chip
>    has a PWON pin that needs to be connected to GND through a
>    pushbutton switch for power-on control.

Just to be sure: Only a short connection to GND is required, is it.
If it needs to be a permanent connection, I'd go for one of these switches: 
The footprint for this switch is fairly generic -- just three pins in 
2.54 mm distance.

> 2. A simple LED that shines upward from the board.

Any SMD LED would do. I kind of arbitrarily chose these 0805 sized chips. 


> 3. What would be a "good" or "reasonable" connector to use for
>    connecting a lab bench power supply?

I like the IL-G series by JAE. These combine smallish size with a good
fit and reasonable high force to disengage and reasonable high current

Two pin pcb header:
Two pin cable receptacle:

My geda footprint:
The corresponding symbol:

If the reasonable high force is not needed, I go for "PSK" connectors.
This is the kind that is used in mother boards to connect the fan. These
fit into the same footprints as the JAE connectors.

The German distributor Reichelt sells a range of both types of connectors
ready made with short cable pig tails.  

If these don't fit due to power requirements, I'd go for the 368 series
by RIACON. These are compatible to the MC 3.81 series by PHOENIX CONTACT.
I buy them from the German distributor Reichelt.

>    I expect my board to draw up to perhaps 2.5 A of current during GSM
>    radio Tx bursts

If it is just short bursts, I wouldn't worry too much. Maximum current for 
connectors relates to mean power over several seconds. 


Kai-Martin Knaak                                  tel: +49-511-762-2895
Universität Hannover, Inst. für Quantenoptik      fax: +49-511-762-2211	
Welfengarten 1, 30167 Hannover 
GPG key:

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