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Paul's "Visible" Educational MPET

This discussion was created from comments split from: MPET Beginners Thread.

Some more of Paul, AC2UQ's progress is lurking in a few other threads like this "Probable Baofeng Mic Connection Guide" one, so be on the look out!

Look at this fantastic wood working skill!




Comments

  • Hi MPET team...well, I've begun to layout my project and, as I mentioned earlier, mount the Ritron on an 8" by 10" piece of plexiglas which will sit in an appropriate sized travel box.

    My major question right now is understanding how the wires from the Microphone; speaker; on/off switch; battery power supply, and (as a back up) DC voltage from and AC source get hooked into the DB-15 Connector.

    For example, if I use a two wire PTT microphone...where does the red wire go and where does the black wire go.

    I don't understand the term "PTT (pull to ground to transmit)" or the term associated with pin 11 "...pull to ground to open squelch", or the term associated with Pin 5 "pull to low to get low power"...

    See....I told you I would 'speak for the beginner'....take heart...I know that I= E/R or is it...???

    Chuck was kind enough to drop by and help me allay my fears about self-electrocution by explaining how a simple transformer uses inductors to change the ac to acceptable level DC...Thanks Chuck! I owe you a 'cuppa'.

    Take care all.

  • edited February 2017

    Here is how you would hookup the speaker.. This pic was taken from K2GOG's presentation at the club meeting. That is a great picture that has it all listed.. Since a speaker is really taking an AC signal you really don't need to worry about polarity. (The cone inside is either pushed or pulled depending on the polarity) However I would always hookup the negative "-" to the ground and the "+" to pin 12. The manufacturer has a reason for labeling them.. The speaker should also be at least 8ohms or higher. I would stick with 8ohms.

    As for the microphone, you have to make sure you have the correct microphone. It is important to look at the Ritron data sheet to make sure the equipment you are hooking up is the correct type. Some microphones are powered, have different impedance and are completely different types that might not work for this radio. We can post more schematics for this as time goes on. But you would do the same thing with the microphone. One is grounded and the other goes to pin 4.

    "PTT" stands for Push To Talk. I took a Baofeng Mic that K2JLV gave me and used the PTT line from that to activate the board and the internal Mic in that. It seemed to work great.

    All items will share the same ground. So pin 15 will have the speaker and the microphone and the PTT switch hooked to that. You can also use any part of the ground on the circuit board as well since it is all the same.

  • I am building a "Visible Radio" mounted and wired using two (or possibly three) 8" x 10" plexiglass (Lexan) sheets so my grandchildren and local high school students can see "Whats under the hood" of a small handheld radio. I will do my best to make this a 'pretty radio' with careful soldering and neat wiring. Students in math and science classes and clubs can see how it all goes together and also see some math formulas and circuit diagrams showing what goes on inside the elements mounted on the Ritron.

    Below are some of the parts I'm proposing to buy with the prices...Aaron and Chester have suggested that we can save money by pooling our purchases, so any ideas are welcome.

    OMARC MPET/Ritron project
    2017.02.08
    Proposed Parts List #1

    Toggle Switches for channel selection, speaker selection, etc.

    1. SPST Micromini Toggle Switch
      3A @ 125 VAC – Radio Shack 275-0624 $3.82

    2. SPDT Micromini Toggle (as above)
      Radio Shack 275-0625 $3.82

    3. DPDT Submini Center-Off Toggle (as above)
      Radio Shack 275-0620 $4.67

    4. SPST Push-On/Off Switch (as above)
      Radio Shack 275-0617 $3.39

    12-Volt Red Lamp Assembly (for visual cues, diff colors etc)
    Radio Shack 272-0345 $1.69

    For battery power supply:
    1. 8 ‘AA’ Battery Holder
    Radio Shack 270-0387

    2. 9v. Battery Snap Connectors
         Radio Shack 270-0324 (Pkg. of 5)
    

    Possible small speaker to be used as alternative to Baofeng
    PTT/Speaker mic per George, K2KMM suggestion

    1. 8-Ohm Mini Speaker (Speaker impedance 8 Ohm-have to check impedance w/Ritron manual per Chester KCYZF suggestion)
      Radio Shack 273-0092

    Take care all,

    Paul

  • Looking forward to read how you set that up. I see 5 wires and the logic really only needs 3, What are those other 2 wires for? They also look twisted, possibly for some reason... INQUIRING MINDS WANT TO KNOW! ;)

  • Okay...I think I have assembled the necessary and sufficient switches, wires, connectors, power supply, and antenna paraphernalia to actually drill a hole or two in the plexiglass surface that will be used to mount my MPET/Ritron transceiver.

    A couple of pics below.


    Thanks for all the advice and counsel from so many OMARC club members...

    I'll keep you informed as it goes and continue to post my questions here.

  • One quick note Paul - What function do you aim to control with those switches? I see 3 of them are only SPST (single pole, single throw) a SPDT (single pole, double throw) switch I always found better to have around as more useful spare and the generally cost the same as a SPST. The manufacturer usually just chops off one lead for you.

  • Ah...thanks Steve....I also have SPDT switches...the three SPST are supposed to choose the channels that you have programmed...good to understand the distinction...do you recommend I switch to the SPDT? I just wanted to keep things as simple as possible.
    Thanks for stimulating my thinking about this issue.

  • So, if you use a SPST, most that will give you is 2 channels, depending how you hook it up to which pin and ground. To get fancy, if you had a SPDT with center off, it would give you 3 channels. This is what I did in my Echolink node.

    If you use a SPDT, it will still only give you two channel operation.

    Of, if you get a "whole bunch of switches", you could conceptually create all the needed logic states to give you all 8 channels, if you dont want to go the rotary route, Chester route, arduino route, or other routes some people may be exploring.

  • Made somes progress yesterday in drilling the holes in the plexiglass and dealing with the practical issues of mounting the board and the switches.

    Standoffs from radio shack worked nicely but found that screws provided were not long enough so had to identify the right size screw to fit into the standoff. Turns out you Size 4-40 Round-head machine screws which come in package of assorted sizes was just what was needed...also purchased small bags of various washers and nuts...it will be nice to have these for future projects. Under $5.00 for a lifetime supply.

    My friend Wynn, who owns the farm adjacent to our home is helping me and we tried to locate mounting hardware from the supply in his giant barn and machine shop.

    We started from big to little.

    On future projects we'll start from small to big...as you can see from the pic below, it took us a while to determine the proper machine screw size. Ah well, it's the journey, not the destination that counts...and it's a hobby!

  • @KC2NDA said:
    Here is how you would hookup the speaker.. This pic was taken from K2GOG's presentation at the club meeting. That is a great picture that has it all listed.. Since a speaker is really taking an AC signal you really don't need to worry about polarity. (The cone inside is either pushed or pulled depending on the polarity) However I would always hookup the negative "-" to the ground and the "+" to pin 12. The manufacturer has a reason for labeling them.. The speaker should also be at least 8ohms or higher. I would stick with 8ohms.

    As for the microphone, you have to make sure you have the correct microphone. It is important to look at the Ritron data sheet to make sure the equipment you are hooking up is the correct type. Some microphones are powered, have different impedance and are completely different types that might not work for this radio. We can post more schematics for this as time goes on. But you would do the same thing with the microphone. One is grounded and the other goes to pin 4.

    "PTT" stands for Push To Talk. I took a Baofeng Mic that K2JLV gave me and used the PTT line from that to activate the board and the internal Mic in that. It seemed to work great.

    All items will share the same ground. So pin 15 will have the speaker and the microphone and the PTT switch hooked to that. You can also use any part of the ground on the circuit board as well since it is all the same.

    @KD2LXQ said:
    Made somes progress yesterday in drilling the holes in the plexiglass and dealing with the practical issues of mounting the board and the switches.

    Standoffs from radio shack worked nicely but found that screws provided were not long enough so had to identify the right size screw to fit into the standoff. Turns out you Size 4-40 Round-head machine screws which come in package of assorted sizes was just what was needed...also purchased small bags of various washers and nuts...it will be nice to have these for future projects. Under $5.00 for a lifetime supply.

    My friend Wynn, who owns the farm adjacent to our home is helping me and we tried to locate mounting hardware from the supply in his giant barn and machine shop.

    We started from big to little.

    On future projects we'll start from small to big...as you can see from the pic below, it took us a while to determine the proper machine screw size. Ah well, it's the journey, not the destination that counts...and it's a hobby!

    @KD2LXQ said:
    Steve, your message is coming through on a different page than our last chat about SPST vs SPDT...
    Anyway...I was planning on using the three switches to create 8 binary choices per Chester's idea...
    each switch only needs, i think a '0' or '1' state...
    A little confusing to do this via these web pages...perhaps we can chat on the phone or on the radio or at the next meeting.
    Thanks
    Paul

    Lets see if this back end fix works. Everything seem in order now?


  • March 1, 2017...making progress.
    Ritron transceiver along with necessary and sufficient switches and 'gozintas' for power and microphone and 'comezoutas' for speaker (in the microphone) and antenna (which is actually both a 'comzinta' and a 'gozouta') all mounted on plexiglas.

    Next step the wiring and the mounting of the plexiglass in a 'visible box'...

    Regarding the wiring...Anybody have the answer to the following questions?

    Question One:

    The power input jack will accept a plug from 8 AA batteries wired in series OR a transformer that supplies 12V DC.

    I have three transformers to choose from:
    One is rated 900 ma Level 3
    The second is rated 900 ma Class 2
    The third is rated 200 ma (no designation of Level or Class)

    Any suggestions on which one of the three transformers I should use?

    Question Two:

    I believe the Baofeng speaker (the output of the speaker/mic) I'm using requires +5 volts. Where do I get the +5 volts from? I see Pin 12 is the Speaker Output. However I do not know what 'comzouta' Pin 12.

    Thanks for reading this and any help or suggestions you can provide.

  • Here is a 'REVERSE VIEW' of the Ritron mounted on plexiglas awaiting wiring and mounting in a 'viewable box'.

  • Paul, I look forward to seeing the completed "visible MPET". You'll have to loom your wires carefully...hehe... Please look for my new thread Re: connecting the Baofeng speaker/mic.

  • April 5 2017 update:

    Finished 12th coat of Tung oil on maple 'visible radio' box...wiring plan complete (except for one detail related to Baofeng speaker/microphone soon to be resolved by Dave and Aaron (thank you guys).

    Should have this first MPET project ready for May OMARC meeting.

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