Looking for someone to design/modify a circuit...

Discussion in 'The Projects Forum' started by John A. Smith, Sep 29, 2014.

  1. John A. Smith

    Thread Starter New Member

    Sep 28, 2014
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    Back ground: I work for a test lab (Fiber Optics and Mechanical Fixture design). I've purchased the Radio Shack Electronics Learners Kit, I've completed all the samples in the books, so I've made LEDs light, horns (including changing the tone) Etc. etc. so I can follow directions.

    I don't get electronics and after 30+ years of people telling me it's like a water pipe, I'm ready to pull my few remaining hairs out. I can't afford to lose my remaining hairs so I've come here in the hopes of finding someone willing to work on, as far as I know, simple circuits.

    From time to time I have a brain wave that will exceed my education and/or experience and I would like to hire someone to design the circuits so I can put them together and test them out. I currently have two projects that have stalled out due to the above and I need to get them moving again. I'll list what the project involves in a vague sense and discuss if someone is interested and how much they would like for the work.

    The first is the most pressing.
    1. Using this chip http://www.aplusinc.com.tw/pro-pic/aivr4208.html or similar.
    2. I need to have a method to load the sound file onto the chip
    3. A speaker
    4. Off board momentary button for activation
    5. Supply voltage higher than 3.5 volts
    6. Fused less than 1 amp
    The second one is a little more interesting I think.
    1. I need to control three (3) small DC motors at different times and different speed on one and pulsed on the other two.
    I'm not really looking for telling me how to do this as I've been trying for about a year now (read Background ;) I know I can do it all manually with a switch and a pot but I'd like it automated. I'd like to work with someone to have the board designed and programmed. I can supply the intended motors. I have most of the mechanical portion completed and this is the final hurdle.

    If someone is interested in the above please feel free to e-mail me at smith*john*albert@g*mail.com (Remove all the (*) from the address.

    Best regards,

    John
     
  2. John A. Smith

    Thread Starter New Member

    Sep 28, 2014
    24
    1
    I found this chip that appears to be like the above and is from Texas Instrument.

    Mouser Part #:
    595-SN74HC251NSRG4
    Manufacturer Part #:
    SN74HC251NSRG4
    Manufacturer:
    Texas Instruments

    or this SN74HC251 Texas Instruments. Basing the design around something I can pick up local has merit as does using a local board house to manufacture and populate.

    being that the data sheet shows some the data on pin outs, I'll pick up a couple.

    John
     
  3. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Welcome to AAC. I may be able to help, but I think we'd all like a little more information on what you're trying to do. The first IC you mentioned appears to be some type of audio chip while the second one is a multiplexer. I'm not sure how they'd be related unless you mean the first IC is for the first project and the second is for the second project.

    For the first project, you want to load a sound file and play back through a speaker by pressing a button, is this correct? What type of file do you want to play and for how long, e.g., voice for 20 seconds, music for 3 minutes, etc.?

    For the second project, can you outline how you want the three motors controlled? For example, do you want to press one button and have all three run at different speeds for a set amount of time?

    How many boards do you need for each project? Is there a target size and/or cost for each board? I know of a way to tackle the first project using a COTS product, but I'm not sure what limitations you need to work within, if any.
     
  4. John A. Smith

    Thread Starter New Member

    Sep 28, 2014
    24
    1
    Elec_Mech,

    Thanks for getting back to me.

    The projects are separate, so I'll go though them by the numbers.

    Project #1
    1. A custom sound file (.wav or other) will need to be loaded into the chip some how. I know they make programmers that you just plug the "board" into, press a button and load the file. I could be wrong, it happens.
    2. The voltage supplied to the board will be 12 volts. So some kind of voltage reducer to the chip will be required.
    3. It needs to be fused. I don't believe the board will take more than a couple hundred mA so a one (1) amp fuse on the board would be nice.
    4. Small speaker, I have not clue on ohms required. I've seen some that have 8 ohms some 16. I'd like the sound a little higher in dB than normal talking volume with decent clarity.
    5. Off the board momentary switch
    6. 14 to 18 gauge wire with plug for the input power
    7. 18-24 gauge for the button wire
    8. 20 second play time, possibly to loop until button is no longer depressed.

    That's what I have so far, anything else will probably be outside of my knowledge.

    Project #2

    1. 12 volt supply voltage
    2. Three motors (Motor A, Motor B and Motor C) Motor A (http://www.ebay.com/itm/Atomik-Veno...Crawlers-/191287869914?_trksid=p2054897.l5659) Motor B and Motor C (http://www.ebay.com/itm/like/230544938850?lpid=82)
    3. Motor a will run at a fixed RPM (tbd) for 15 minutes.
    4. Motor B will turn on and off for 5 seconds with a one minute off for 15 minutes.
    5. Motor A will increase in speed to a fixed RPM (tbd)
    6. Motor C will turn on and off for 15 seconds with a 15 second off period for 5 minutes.
    7. Turn off.
    8. LEDs would be nice so a visual on which timing sequence it's on.

    I really can't think of too much more to add.

    Let me know,

    John
     
  5. ISB123

    Well-Known Member

    May 21, 2014
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    I'll try to figure something out for the 1st project since I have some free time.
     
  6. RichardO

    Well-Known Member

    May 4, 2013
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  7. John A. Smith

    Thread Starter New Member

    Sep 28, 2014
    24
    1
    RichardO,

    I went and purchased three of the Radio Shack modules last week. The play button is on the board. So I've taken the cover off the button and will be soldering leads onto the board to move the button. So it mostly does what I want, but has a microphone attached. They are also 9 volts, I'll need 12 volts. I powered one with 12 volts and it didn't go up in smoke, but I'd rather be safe than sorry.

    I've seen several of the products like the one listed in Digikey. At $15.00 the price point is way to high.

    I've purchased ten (10) of these SN74HC251NSRG4 to start playing with. Even on a custom board in low numbers (less than 1,000) I should be able to populate it around $5.00.

    Thanks,
     
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,172
    397
    Line 6, project # 2, On-Off for 15 sec, with off of 15 sec = mighty short on.
    Current rating of motors??
     
  9. ISB123

    Well-Known Member

    May 21, 2014
    1,239
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    Does the MCU has to be the one you posted or it can be some other like ATtiny?
     
  10. John A. Smith

    Thread Starter New Member

    Sep 28, 2014
    24
    1
    Bernard,

    Sorry for the confusion, it will be on for 15 seconds, off for 15 seconds. I hope that helps.

    I'll run outside and power them up and give you the Voltage and amps. Shouldn't take me more than a few hours ;) I actually have a 12v power supply set up to run though a Dr. Watson that will measure the power requirements. Be right back.

    John
     
    Last edited: Sep 29, 2014
  11. John A. Smith

    Thread Starter New Member

    Sep 28, 2014
    24
    1
    ASB123,

    I'll assume the MCU is micro control unit ( or from the movie TRON?) I'm not tied to any one chip, I just need one that works, is highly reliable (I do HALT Testing at my full time job) and readily available. I've seen chips anywhere from 0.05 up to 15.00, not sure what it takes quite honestly and will defer to someones expertise.

    Best regards,

    John
     
  12. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    There are lots of options for sound devices. Personally, I'd use a ready-made device such as this. It meets most of your criteria: allows you to load a wav file (or convert an existing wav file to load into it) via USB, comes with its own speaker, and has an external switch (which can can replace with a longer cord or a different switch or both). It operates off of 4.5-5.5VDC, so a regulator IC or a Zener diode would need to be added to accept 12VDC. You'll need a second board anyway to fit connectors or terminals to accept the wire sizes you've specified.

    There are ways of rolling your own, but I'd have to spend a lot of time researching just how to do so at a lower price than a COTS solution. I will watch what ISB123 comes up with with interest.

    The second project can be done with a microcontroller. Almost has to be to keep the circuit small and low cost. I believe I could do this with a PICAXE. If we go that route, you can easily make changes to the program yourself easily without buying expensive or loading complicated software.

    Can you step through the motor operation in more detail?

    As I understand it, motor A runs at a set RPM for 15 minutes continuously. After 15 minutes it will change speed (RPM) and . . . ?

    Motor B will run for 5 seconds, stop for one minute, then repeat this cycle until 15 minutes have passed then stop completely. Is this correct?

    Motor C will run for 15 seconds, stop for 15 seconds, then repeat this cycle until five minutes have passed then stop completely. Is this correct?

    LED indicators are a cinch.

    Do the RPM's of either motor B or C need to be fixed or can they run full bore? As they are pumps, I assume full bore, but want to be sure.

    What quantities of each project are you ultimately planning to produce? This helps with things like buying ready-made vs. designing your own. Each has their pros and cons.
     
  13. John A. Smith

    Thread Starter New Member

    Sep 28, 2014
    24
    1
    Bernard,

    Motor #1, 12 Volt supplied, Running no load amps 0.10 amps, almost stalled 0.28 amps. The one I have is a gear reduction but the motor is the same type.

    Motor #2 and #3 12v supplied, running no load 0.61 amps, start up over one amp, I couldn't put a load on it without shooting water all over the place, sorry.

    More than happy to supply any other information.

    Best regards,

    John
     
    Bernard likes this.
  14. John A. Smith

    Thread Starter New Member

    Sep 28, 2014
    24
    1
    Elec_Mech,

    Project #1
    For a price point or design I was hoping for something like this: http://www.alibaba.com/product-detail/Greeting-card-sound-module-musical-sound_1326576896.html I'd rather have it made in America, I'm a Marine Vet, so this country and buying here suits my personal belief systems and if it only cost a buck or two more, who cares. ;) Maybe we'll hire more local talent and my taxes will go down ;) I'd prefer one board, if possible, size really isn't an concern as long as it's less than a breadbox. I'll need the heavier wire for the power, I'll defer to people who know these things, I'd prefer stranded for flexability, I don't care about EMI, I can have the boys in the other dept test it for EMC or EMI the black art of electronics I'm told.
    Initial quantity = 500 to 1,000

    Project #2
    I have no idea what a PICAXE is, garden tool?
    Motor A will run at a fixed RPM for the 15 minutes with Motor #2 spraying "The Thing". After the 15 minutes the RPM will increase to (tbd) and motor #2 will spray "The Thing". After 5-10 minutes (TBD) it will shut off.

    Motor #2 and #3 will run full bore.
    Initial Quantity = 10 or so. I still have to check the market, I think it's huge, but what do I know. It has to work before I can show it to people. ;)

    Hope that helps,

    Best regards,

    John
     
  15. ISB123

    Well-Known Member

    May 21, 2014
    1,239
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    Since you are willing to upload code to the IC I think that ATtiny85 would be the cheapest version to do and is pretty simple.
     
  16. John A. Smith

    Thread Starter New Member

    Sep 28, 2014
    24
    1
    I looked up the ATtiny85, that looks really simple. 0.75 for 100 of them isn't a bank breaker either.

    Now a speaker and button, viola.
     
  17. John A. Smith

    Thread Starter New Member

    Sep 28, 2014
    24
    1
    Stop the Train.

    Project #1

    I received some feedback late last night from three of the people I had using the mock-ups. Although it worked as I had planned the implementing of device will need to be re-thought. Seems what I consider a non-issue is an issue. I'm looking for some way to modify the design to be easier to install in the intended application. On hold till.........

    Thank you

    Project #2

    I've started assembling the mechanical parts and with enough garage time this weekend I should have mostly complete, God willing and and the creek don't rise.

    best regards,

    john
     
  18. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    In Project #2, motor 1 is a Johnson-type brushed motor, and motors 2 & 3 are windshield washer pump motors, indicating you're planning on pumping and/or spraying some kind of liquid.

    Are you aware that the Johnson motor:
    1) needs dry air circulating around and through it
    2) has brushes that will make small sparks, so it can't be used near flammable gases/fluids
    3) will fail rapidly if exposed to moisture
    4) will need periodic replacement due to the non-replaceable brushes wearing out

    Just so that you are aware of these types of things - since you haven't stated what the assembly's intended purpose is, it's a bit difficult to guess.

    S/F
     
  19. John A. Smith

    Thread Starter New Member

    Sep 28, 2014
    24
    1
    Sgt. Wookie,

    Nice Sword, although I never purchased one, I've carried them many times. Still have my earlobes.
    Johnson motor
    1. Yes, these will be isolated and ventilation provided
    2. Yes, a capacitor across the leads and cans will be done. The fluids being pumped are not flammable liquids (NSA concerns there. ;) )
    3. Yes, but should not be exposed to outside ambient humidity. I'm open to suggestions.
    4. Yes, I've found some that have replaceable brushes. Going to a brushless motor really increases the cost per unit. I'm not sure if the motor controller could be built into the control board. Might make things easier, might not.

    S/F

    John
     
  20. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,172
    397
    Just for comparison with uC, roughly laid out # 2's timing using IC's. A 4060 would be nice, but stage 11 is not available so used 4020, 12 stage counter with external clock with period of .9375 s. With 3 ANDs & an OR we have a repeating 5.6 s hi with 1 m period to control motor B, & will run as long as motor A is running.
    Motor C needs 2 AND's & a flip-flop to give a square wave with 30 s period, reset at 5 m with 1 AND. Motor A, for 15 m speed change, 1 AND, & another AND for 30 m. With some more misc. ICs
    Gets messey, does it not?
     
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