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2017-09-10, 22:19
(This post was last modified: 2017-09-10, 22:49 by RichoAnd.)
When I look back, you seem to have been unlucky choosing power supply.
I think a high power switching mode should be tampered with a passive load of at least 10% of the max before it behaves properly
We use a small switch mode power supply (typical 1-2A) designed for small electronics.
To avoid power loss, we use switchmode, but a linear is much better.
I usually use a 6-9V switchmode with a low drop linear afterwards.
I know BLUE could be protected much more, it is also considered (Both static input voltage / wrong polarity / high voltage spikes / RF-protection etc. ) - BUT it costs a lot and occupy space.
Should it be fool proof, it must be delivered complete including PowerSupply, all antennas and connecting cables and with connectors that can not be confused.
It's an amateur project, but not for first-time soldering.
We try to make it easy and relatively cheap, but we expect reasonable skills in processing electronics. - Sorry if we forgot to tell?
/Richo
P.S. BLUE use about 0,5A, and a good 1A PS can do the job.
Remote sensing is not necessary if you use a relatively short and thick cable.
IF you use remote sensing, remember that it must be able to fail without the voltage rising too much (1KOhm connection already inside the power supply )
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2017-09-10, 23:56
(This post was last modified: 2017-09-10, 23:58 by readbueno.)
Hi Richo, Please don't take my remarks too much to heart. I have been playing with radio and kits for quite a few years (Fiftyish more or less :-)) and I know some of the pitfalls!
I don't think that it would actually cost much more to add some protection, after all at 200 euros a pop this kit not exactly cheap and the space is not too much of an issue, as there is still some spare area up next to the beeper. I think that the connections are already sufficiently varied that most people would have to be really awkward to get them mixed up and I think with the usb mini b it is not possible to connect it the wrong way around.
Maybe I am just a little sensitive at the moment. :-)
My soldering is certainly not bad although with advancing age and the rush for tiny components it is not likely to get much better.
The trouble with the plethora of small switch mode psu's that come with every small thing that you buy these days is that they are a bit unpredictable, even unreliable!
I was certainly disappointed that my station only lasted 2 days, but I believe that this is a good project and so I have bought another board and I will take even more care and hope that it will survive a slightly longer this time.
Egon has asked me to send him the the faulty board and this I will do.
Kindest regards,
Brian.
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Sorry, I generalized - It was not specifically addressed to you.
I think you have been unlucky, not lacking skills :-)
/Richo
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Thank you for that Link.
Brian.
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A linear power supply using a 7805 is cheap and simple.
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Hi Mike, I have ordered some LM1085s which is the lower drop out version of the 7805 and I think it gives a more comfortable current output level as well.
I will play with them when they arrive, on a breadboard with a 2" heat sink, starting with the basic circuits from the data sheet. :-)
Brian.
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(2017-09-11, 19:00)readbueno Wrote: Hi Mike, I have ordered some LM1085s which is the lower drop out version of the 7805 and I think it gives a more comfortable current output level as well. ...
Hi Brian, What do you mean by "a more comfortable current output level"?
I am considering a linear 7805 PS instead of this tablet charger. I notice 25 mV or so of ripple on the last two channels (which have a separate ADC than the first two). I don't want an adjustment, but would the 1085 be better than a 7805?
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Hi Mike, Here are the two data sheets. Both the regulators can be adjusted by small amounts I think. The limit with both appears to be related mainly to temperature but the LM1085 has about twice the power output and better regulation to temperature graph. So it should run cooler and provide better regulation and allow for a better margin if change on the input.
LM7805 Data sheet
https://www.sparkfun.com/datasheets/Comp...LM7805.pdf
LM1085 Data sheet.
http://www.jameco.com/Jameco/Products/Pr...279365.pdf
There are others of course everyone seems to have there own favourite manufacturer and just about everyone makes these handy little devices.
http://www.ebay.com/itm/10pcs-New-LM1085...SwGotWkho5
Like the 78 series they do come in all the standard voltages so just make sure that they send you the ones that you want.
Mouser and Farnell also have them, but at five times the price and for here at least, a minimum $12.00 postage/packing charge as well.
However, up to a month to come from China and two days from mouser!
Brian.
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Thanks for the info, Brian.
Personally, I would never buy active devices of any sort from China. I've read too many awful experiences from hams on eHam and QRZ.
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Hi Mike, I believe that no matter where you buy them, they are nearly all made in China, Taiwan, South Korea, India or Japan?
I have bought a fair amount of stuff over the last few years off eBay and on the whole it has been pretty good.
Sometimes the hand soldering is not very good, but even I have had difficulty with even good quality Lead free solder and soldering them again with decent solder cures most of the problems. :-)
Considering the amount of consumer stuff that is actually being made in China these days, the quality is not worse than anywhere else, as long as you keep away from the very cheap stuff.
Brian.
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