[minima] Re: Linear Output Filter Switching
- From: Sunil Thomas Thonikuzhiyil <vu2swx@xxxxxxxxx>
- To: minima@xxxxxxxxxxxxx
- Date: Sat, 1 Feb 2014 18:29:53 +0530
Why not use a cheap I2c converter for LCD display and save lot of pins. It
costs only $2.5
See this
http://www.aliexpress.com/item/Free-Shipping-New-5V-IIC-I2C-Serial-Interface-Board-Module-For-Arduino-1602-LCD-Display/982812679.html
Sunil
VU2SWX
On Sat, Feb 1, 2014 at 5:20 PM, Frank <w4nhj@xxxxxxxxxxx> wrote:
> Farhan and all,
>
> It seems like the Arduino Uno chip is just about maxed out. The mega2560
> chip has much more capacity, but it is very expensive, approximately $15 US
> and is SMD which would make it hard to solder. Perhaps a second Arduino
> Uno chip to give many more features in the future. Perhaps another Si570
> for a variable BFO, CW keyer, etc.. Of course these would be options
> enabling one to build the basic Minima cheaply and add as money allows.
>
>
> Frank - W4NHJ
>
> -
> On 2/1/14, 12:00 AM, Ashhar Farhan wrote:
>
> Mark,
>
> I have been mulling over this ... and I am trying to balance quite a few
> things here.
>
> 1. Can we make do with just four filters? I have attached a screenshot
> of a simulation I ran (both these programs are available on the EMRFD CD).
> As you can see, a filter can be cut for 7 and 10 mhz. The 7 mhz's second
> harmonic at 14 is down by 25db. Which means, if we don't distort the linear
> too much, we can get more 43 db suppression of the harmonics. If you guys
> agree to this , then, I propose as follows :
> 1st filter for 3.5 MHz
> 2nd filter for 7-10 mhz
> 3rd filter for 14-18 mhz
> 4th for 21-28 mhz
> These will have to be three section filters, which is alright. A 1-of-4
> decoder like 74LS139 could do the switching with just 2 lines.
>
> 2. The switching of the main filters is at variance with this scheme.
> so, we will have to use a dedicated line (as we are doing now) to switch
> these filters.
>
> 3. There is a third line A0 (pin 23) that is unused. this can be used to
> switch in a higher bandwidth filter (more than 10 Khz). with this filter,
> the broadband audio can be fed to an 'SDR' back-end like linrad. The serial
> port can provide the tuning control.
>
> - f
>
>
> On Sat, Feb 1, 2014 at 7:01 AM, Dan Reynolds <on30ng@xxxxxxxxx> wrote:
>
>> I'm not any kind of an expert but could you use a Microchip MCP23017
>> I/O expander on the 5 V side of the I2C bus. I was thinking something like
>> I saw on the Tronixstuff page here:
>>
>> http://tronixstuff.com/2011/08/26/tutorial-maximising-your-arduinos-io-ports/
>> Instead of a LED an I/O line could drive a transistor to drive a relay(?).
>> Then the code could "watch" the frequency and as it changes the output
>> line for that particular LPF could be switched.
>>
>> Or could you use a 74HC595 to accomplish the same thing.
>>
>> http://tronixstuff.com/2010/04/30/getting-started-with-arduino-chapter-four/
>>
>> I was going to approximate the Minima front panel with a bare bones
>> Arduino and some parts and see what I could dream up.
>> I don't really know what I'm doing. I'm just muddling through trying to
>> patch bits and pieces together...
>>
>>
>> 73
>> Dan -- KB9JLO
>> https://sites.google.com/site/on30ng/
>>
>>
>> On Fri, Jan 31, 2014 at 6:10 PM, Wayne McFee <nb6m@xxxxxxx> wrote:
>>
>>> Hi Mark,
>>>
>>> If the three outputs were set up as you suggest, a Picaxe chip could be
>>> programmed to control either individual relay driver transistors or a relay
>>> driver chip like the 2903(?).
>>>
>>> I've been using that arrangement for filter selection in a homebrew rig.
>>>
>>> Or, if one of those output lines could be programmed to output a stepped
>>> voltage such as that provided by the FT817 for bandswitching info, that
>>> makes the programming even easier.
>>>
>>> Wayne NB6M
>>>
>>>
>>> > On Jan 31, 2014, at 1:24 PM, Mark G0MGX <mark.g0mgx@xxxxxxxxx> wrote:
>>> >
>>> > Farhan & Team,
>>> >
>>> > I can see that we have provision in the schematic for 3 digital
>>> outputs for band selection, but can only see one of these (BAND_HI - pin 11
>>> - Arduino D5) being used within the function "setBandswitch". It is this
>>> function that currently selects the LPF used based on frequency.
>>> >
>>> > We could set the state of the three outputs based on frequency
>>> something like this:
>>> >
>>> > <Filter Ideas.png>
>>> >
>>> > But someone far cleverer than I would need to explain how to create
>>> relay on/off switching based on the logic states of the three lines - I
>>> have no idea how to do that!
>>> >
>>> > If we were to implement something like this was the intention to use
>>> these additionally switched filters in RX as well as TX?
>>> >
>>> > I would be interested in your thoughts and ideas on how you saw this
>>> working before I head down the wrong road with my construction!
>>> >
>>> > Many thanks,
>>> >
>>> > Mark
>>> > G0MGX
>>>
>>>
>>
>
>
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