[minima] Re: Linear Output Filter Switching
- From: Wayne McFee <nb6m@xxxxxxx>
- To: "minima@xxxxxxxxxxxxx" <minima@xxxxxxxxxxxxx>
- Date: Thu, 6 Feb 2014 09:01:55 -0800
Hi Mark,
I would suggest using the Omron 2Amp DPDT relays to switch the filters and
parallel the two poles.
Wayne NB6M
> On Feb 6, 2014, at 3:52 AM, Mark G0MGX <mark.g0mgx@xxxxxxxxx> wrote:
>
> Hi Team
>
> I've done a bit more work on the output filter switching using a 4028 (which
> arrived today!).
>
> The wiki is updated:
>
> http://www.hfsignals.org/index.php/Final_Output_Filters
>
> Including a link to a simple sketch to try and illustrate how it works and
> enable others to prototype the ideas as I have.
>
> There will be more on this topic from me....
>
> Mark
> G0MGX
>
>
>> On 04/02/2014 19:05, Dan Reynolds wrote:
>> 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
>>>>>>>> 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>
>>>>>>>> >> Sent: 01/02/2014 05:00
>>>>>>>> >> To: minima@xxxxxxxxxxxxx <mailto: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>> 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>> 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>> 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
>>>>>>>> >>
>>>>>>>> >>
>>>>>>>> >>
>>>>>>>> >
>
Other related posts:
