[minima] Re: Parts list spreadsheet, still work in process

  • From: "Tayloe, Dan (NSN - US/Tempe)" <dan.tayloe@xxxxxxx>
  • To: "minima@xxxxxxxxxxxxx" <minima@xxxxxxxxxxxxx>
  • Date: Sun, 16 Mar 2014 22:15:27 +0000

While the simple approach is nice from a minimalistic perspective, with 100 
ma@5v for the LCD back light and 90 ma@3.3v for the Si570, you could cut back 
perhaps 50 ma of the 100ma 5v backlight and 60 ma from the Si570 if there were 
allowances to feed 5.5v from a switching regulator into a 5v low drop out 
regulator and 3.8v from a switching regulator into 3.3v LDOR.

It would be a nice option anyway, cutting out 110 ma@12v of un-needed current 
drain and heat.


-          Dan

From: minima-bounce@xxxxxxxxxxxxx [mailto:minima-bounce@xxxxxxxxxxxxx] On 
Behalf Of ext Mvs Sarma
Sent: Saturday, March 15, 2014 10:22 PM
To: minima@xxxxxxxxxxxxx
Subject: [minima] Re: Parts list spreadsheet, still work in process

IMHO, Two numbers of 39 ohms in series would suffice. They occupy less space, 
work out cheaper than a heat sink. The resistors can  be placed vertically in 
same location and joined at the top.

On Sun, Mar 16, 2014 at 10:46 AM, Mac A. Cody 
<maccody@xxxxxxx<mailto:maccody@xxxxxxx>> wrote:
It is better to keep the backlight LED on the 5V buss. Placing it on
the 12V buss would require a larger resistor in order to provide the
appropriate current for the LED.  For example, assume the LED has a
typical forward voltage drop of 4.1V for a current of 100mA.  For a
5V supply, the resistor needed for the current would be 9 ohms.  The
resistor would dissipate 0.09 Watts of power.  For a 12V supply, the
resistor needed for the current would be 79 ohms.  The resistor would
dissipate 0.79 Watts of power.  Consequently, a physically larger and
more expensive resistor would be needed.  What I would do, though, is
provide a means to switch the power to the LED backlight in order to
conserve power, especially if operating in the field.

73,

Mac AE5PH

On 03/15/2014 11:49 PM, Mvs Sarma wrote:
Perhaps, we can mod the back lit section and connect it to 12V instead. BUT the 
series resistor should be re  evaluated. Thus we can manage 7805 without 
heatsink on digital board.

On Sun, Mar 16, 2014 at 10:16 AM, Thomas Sarlandie 
<thomas@xxxxxxxxxxxxx<mailto:thomas@xxxxxxxxxxxxx>> wrote:
Just looked at your spreadsheet. One more thing: You have a 78l05 on the RF 
board for the KISS mixer bias but you will also need a 7805 (to220 package) for 
the arduino board. Make sure you put a heatsink on it. The LCD backlight uses a 
lot of current and that regulator needs to dissipate 12-5=7v * the current used 
by all your circuit.

Do not share the same regulator for both functions.




On Sat, Mar 15, 2014 at 9:41 PM, Thomas Sarlandie 
<thomas@xxxxxxxxxxxxx<mailto:thomas@xxxxxxxxxxxxx>> wrote:
Jeremy,

Great initiative! Some replies in text based on my experience building it.

Hello,
I've systematically gone through the schematic and made a comprehensive parts 
list from it. I'm hopeful this will be useful to both myself and others!

https://docs.google.com/spreadsheet/ccc?key=0AkbVpmVim4O7dGM2SGZaYkJvTU1DNnloak1RZnpDZ2c&usp=drive_web#gid=0
I still have many questions that I want clarification on though. If anyone can 
give more detail about the following please reply:

  1.  Is there a recommended inductor type for all of the filter components? (A 
toroid type, etc.)

I have used what Mark recommended and just had to slightly adjust the number of 
turns. Maybe because my magnet wire was smaller.

I thought this information was on my website but nope :( I just added it.

Value

Qty

Core

N-Turns (Mark)

N-Turns (Thomas)

.33 uH

2

T37-6

10

9

.39 uH

2

T37-6

11

10

.66 uH

2

T50-2

12

10

.78 uH

3

T50-2

13

11

3 uH

3

T33

25

24




  1.  Can the 3u inductor near T3 be the same type as the inductors in the 
filter?
I guess you are referring to the inductor labelled "RFC" on Farhan's schematic. 
Farhan said: "The RFC is 10 turns on FT37-43" According to 
toroids.info<http://toroids.info>, that is 35 uH.

So no you cannot use the same inductors. And where did you get the value 3uH?


  1.  What is the 'BAND SELECT' part connected to PD6 and PD7 of the Arduino?
This is a connector that would go to your power amplifier to switch different 
band-pass or low-pass filters depending on the band that you are on. The 
original idea was to use those 3 bits to select one band (3 bits = 8 
possibilities). We have since then explored other options and Farhan has chosen 
the CD4017 option.

Read "Bandswitching the low-pass filters" on the RF386 page for more info on 
the new design that will only take one line:
http://www.hfsignals.org/index.php/RF386

  1.  Can all 4 relays be of the same type? I know nothing about relays; what 
should I be looking for?
The two relays in the LPF and the relay in the BFO are SPDT. The one that 
switches the audio and tx/rx (bottom of the schematic) is a DPDT. You could 
replace it by two separate relays if you wanted to stick to just one model.

The most important characteristic is the voltage of those relays. Get 12v dc 
relays. They should be adapted to small signals. Some are labelled for "RF 
signals" and are a bit more expensive but I am not sure it makes a huge 
difference for us.

I have used BESTAR BS-102B for the LPF and the BFO. Bought them in a surplus 
where they were the cheapest 12v small size relays. They seem cheap online too:
http://www.alibaba.com/showroom/bs--102b--12vdc-bestar-standard.html

For the DPDT I have used OMRON G6H-2.

You can see pictures of them on my minima webpage.

  1.  There are capacitors labeled "0.01" near Q20, but they don't have a unit. 
What size are these capacitors?
Micro Farads.

  1.  There are unmarked electrolytic capacitors. One is near Q11; what size 
are these unmarked electrolytic caps?
I have asked about those a few times and did not get a clear answer. I have 
read articles that claim that only the "+" symbols call for electrolytics and 
that it is perfectly fine to use the curved+flat symbol for ceramics. This 
matches what you see on the schema: the electrolytics do have a "+" sign.

I have used the same capacitors than everywhere else for those (0.1 uF). I 
would love to hear from Farhan why some have a different symbol!

  1.  There are electrolytic capacitors labeled +50, are these actually 50u?
Yes. But I have used 47uF. Much easier to find.

  1.  There are four 22p variable electrolytic capacitors; Are these trim caps? 
Can I see an example? What am I looking for?
Look on my pictures or mark's pictures:
http://www.sarfata.org/ham/images/minima-lpf-top.jpg

  1.  I see 2 10k trim pots, a 1 turn 10k variable pot and a 1 turn 100k pot. 
Is this accurate?
Yes. You might want to get a logarithmic pot for the 10k because it controls 
the audio but the 100k must be linear.

  1.  There is a crystal labeled 16M connected to X2 of the Arduino. Is this a 
16Mhz crystal?
Yes.

Enjoy!

73,
thomas

Thank you very much!
73 de K2CHA

--
Jeremy Chase
http://twitter.com/jeremychase





--
Regards
Sarma





--
Regards
Sarma

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