[minima] Re: Linear Output Filter Switching
- From: Dan Reynolds <on30ng@xxxxxxxxx>
- To: minima@xxxxxxxxxxxxx
- Date: Tue, 4 Feb 2014 13:05:17 -0600
Thanks Mark. I'm learning a lot but you know how it is when you're dreaming
- you never learn fast enough. I'm pouring over tutorials on the web to
help me understand better.
I think I know what the schematic will look like but I just want to see it
from a more credible source than my brain!
I hope to have the Boarduino and the front panel all mocked up by the
weekend. I have an Si570 on the way. I'm going to use the WB6DHW Si570
board for the level shifter circuit.
http://wb6dhw.com/For_Sale.html#Si570
That should also keep me out of trouble with modifying that one library...
Then I can start mocking up / playing with the LPF selection logic
perhaps...
Thanks everybody. This is a neat project and I'm going to learn a whole lot!
73
Dan -- KB9JLO
https://sites.google.com/site/on30ng/
On Tue, Feb 4, 2014 at 12:53 AM, Mark G0MGX <mark.g0mgx@xxxxxxxxx> wrote:
> Hi Dan & Team
>
> When I get the CMOS chips I have ordered I will publish to the Wiki the
> schematic for filter switching, details for interfacing to the bare bones
> Arduino and also publish my suggested code modifications/changes to control
> the switching based on radio frequency. I will also put extensive comments
> into the code to explain what's going on.
>
> The ULN2803a does look like a great option - I have just ordered some of
> those from eBay - so I will experiment with this option also in due course.
>
> Mark
> G0MGX
>
>
>
> On 03/02/2014 22:18, Dan Reynolds wrote:
>
> I wish someone could draw up a schematic and show a modified codes
> segment so someone dense like me can get his head around it.
>
> I looked at that CD4028 example and Mark, your second chart is starting
> to make sense...
> I think the ULN2803a is a good idea too.
> Do you ground the unused inputs on that chip?
> And then I assume the common on the output side would go to +12V for
> relay energizing power.
>
> This project could be an excellent learning project for me all the way
> around! :-)
>
> 73
> Dan -- KB9JLO
> https://sites.google.com/site/on30ng/
>
>
> On Sun, Feb 2, 2014 at 12:51 PM, Wayne McFee <nb6m@xxxxxxx> wrote:
>
>> Mark,
>>
>> I'm using a ULN2803a Darlington Driver chip to drive the relays for LPF
>> selection in a homebrew amp. These have the back current diodes in them,
>> so no external diodes needed across the relays.
>>
>> Just a thought, as it saves building individual drivers with
>> transistors (like I did in another project).
>>
>> Wayne NB6M
>>
>> On Feb 2, 2014, at 6:54 AM, Mark G0MGX <mark.g0mgx@xxxxxxxxx> wrote:
>>
>> Hi Gang
>>
>> I've completed a proof of concept of the output filters today; it uses a
>> 74141 as a BCD to individual selection connected to a 74LS00 used as NOT
>> gates or inverters for the output lines.
>>
>> I can control this OK from the Arduino code, so I have ordered some of
>> these CMOS 4028s as this has a HIGH output state when an output is selected
>> whereas the 74141 is a LOW state when an output is selected (I have used
>> 74141 previously to ground cathodes of Nixie tubes!). This is the logic of
>> the chip:
>>
>> <74141 logic.png>
>>
>>
>> So I now wait for the postman before I can complete the filter output
>> stage.
>>
>> I am thinking that we might like options in the code/filters as it seems
>> to me we need to keep the current RX filter selection pin usage, but also
>> use this for filter selection. We can go with very simple as suggested by
>> Farhan and have 4 filters, or we can have 5 to include either top band or
>> 60M (5MHz).
>>
>> I will post more when I have the final design and code mods once built
>> and tested. I am definitely going with a 3 line BCD output from the Arduino
>> processor to select filters based on radio tuned frequency. This will be
>> accomplished in the existing function "setBandswitch". Maybe (only maybe)
>> something like this:
>>
>> <Filter Ideas3.png>
>>
>>
>> In the code we will declare three digital outputs (including the existing
>> BAND_HI) and set all three each time we change frequency, the state (HIGH
>> or LOW) of each output will be dependent on frequency and in accordance
>> with the truth table and output usage above.
>>
>> Mark
>> G0MGX
>>
>> On 01/02/2014 18:47, Mark G0MGX wrote:
>>
>> very good. That CMOS chip used in the link looks the same as the TTL
>> 74141 - but I am no expert.
>>
>> This does seem to be the way to go
>> Mark
>> G0MGX
>>
>> On 01/02/2014 18:24, mpcharlton@xxxxxxxxxxx wrote:
>>
>> Mark
>>
>> Have a look at this halfway down the page...
>>
>> http://www.vk5tm.com////homebrew/filter/filter.php
>>
>> Mark
>> G6ZQS G-QRP 2247
>>
>>
>>
>>
>> *-------Original Message-------*
>>
>> *From:* Mark G0MGX <mark.g0mgx@xxxxxxxxx>
>> *Date:* 01/02/2014 17:29:09
>> *To:* minima@xxxxxxxxxxxxx
>> *Subject:* [minima] Re: Linear Output Filter Switching
>>
>> Isn't this:
>>
>> http://www.g3ynh.info/digrdout/74141.html
>>
>> exactly what we need to go from Binary outputs on our 3 digital lines to
>> individual relays controlling filters?
>>
>> Mark
>> G0MGX
>>
>>
>> On 01/02/2014 15:26, farhanbox@xxxxxxxxx wrote:
>> > Mark,
>> > There's something not right about the curve. The stopband is quite
>> nominal. You must get atleast 60 db stop-band.
>> >
>> > Sent from BlackBerry® on Airtel
>> >
>> > -----Original Message-----
>> > From: Mark G0MGX <mark.g0mgx@xxxxxxxxx>
>> > Sender: minima-bounce@xxxxxxxxxxxxx
>> > Date: Sat, 01 Feb 2014 13:47:38
>> > To: minima@xxxxxxxxxxxxx<minima@xxxxxxxxxxxxx>
>> > Reply-To: minima@xxxxxxxxxxxxx
>> > Subject: [minima] Re: Linear Output Filter Switching
>> >
>> > Hi Team
>> >
>> > I've started the output filter Wiki page here:
>> >
>> > http://www.hfsignals.org/index.php/Final_Output_Filters
>> >
>> > and have so far put info on 4, 11 and 19MHz cut off Low Pass Filters. I
>> > am very unhappy with the 19M filter sweep, so will let you guys take a
>> > look before doing any more. The next filter needs to be 30M cut off - we
>> > already have one of those!
>> >
>> > As an aside I have dug out my CD from EMRFD and mine is a 2002 version
>> > of the software which I can't find a filter designer? I can enter values
>> > myself but cant get the software to come up with the filter for me -
>> > hence I have stuck with what I know and used QUCS for my designs.
>> >
>> > I do think that we could still use the existing D5 line for output _*as
>> > well as*_ the existing input filter switching just so long as the line
>> > stays HIGH for > 15MHz and LOW for <= 15MHz. This would give us room for
>> > a 1.8M filter and another if we find we need i. I have only focused on
>> > those highlighted yellow below, but clearly with the three digital lines
>> > we could have up to 8 filters if we needed them.
>> >
>> >
>> >
>> > I personally like the idea of simple logic chip or BCD type logic to
>> > control relays as I feel that we want to avoid more programming and
>> > complexity where it's not needed. The 74LS139 idea is a great one and
>> > probably the way I plan to go, but lets see what we decide.
>> >
>> > I've tried to explain some of this in the Wiki - please take a look and
>> > lets decide between us how we are going to do this part of the project.
>> >
>> > We could of course go with the idea of a separate amplifier completely,
>> > maybe with the tubes others are suggesting! I've never built anything
>> > with tubes....
>> >
>> > Mark
>> > G0MGX
>> >
>> > On 01/02/2014 06:48, Mark wrote:
>> >> Thanks to everyone for the suggestions and ideas.
>> >>
>> >> If we go with 4 filters have we scrapped top band?
>> >>
>> >> I'll try and run some designs for the four suggested filters and build
>> >> some prototypes and stick the results on the wiki.
>> >>
>> >> We can then decide and discuss what we think we should do.
>> >>
>> >> M
>> >>
>> ------------------------------------------------------------------------
>> >> From: Ashhar Farhan <mailto:farhanbox@xxxxxxxxx <farhanbox@xxxxxxxxx>>
>> >> Sent: 01/02/2014 05:00
>> >> To: minima@xxxxxxxxxxxxx
>> >> <mailto:minima@xxxxxxxxxxxxx<minima@xxxxxxxxxxxxx>
>> >
>> >> Subject: [minima] Re: Linear Output Filter Switching
>> >>
>> >> 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
>> >> <mailto:on30ng@xxxxxxxxx <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
>> >> <mailto:nb6m@xxxxxxx <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
>> >> <mailto:mark.g0mgx@xxxxxxxxx<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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