1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

making 14V programming voltage

Discussion in 'Microcontrollers' started by mik3ca, Dec 20, 2017.

  1. mik3ca

    mik3ca Member

    Joined:
    Jun 24, 2017
    Messages:
    274
    Likes:
    1
    I just bought a few w77e58 DIP IC's because I needed an 8051 micro with two UARTs. Sadly, this particular chip doesn't have ISP but I'm lucky to still own a parallel port on my computer to make a programmer.

    The datasheet for this chip suggests I use 12.5V on VPP for programming voltage and about 14.5V on VPP for erase voltage.

    I have a couple thoughts in mind for generating the voltages.

    1. Buy power adapter that's 18+V and feed it through 3 voltage regulators in parallel so output of each regulator has 5, 12.5 and 14.5V respectively.

    2. Run everything off 5V but somehow make some sort of step-up voltage converter (like a diode/capacitor ladder? would that work)?

    I'm trying to think of the best approach here.
     
  2. MikeMl

    MikeMl Well-Known Member Most Helpful Member

    Joined:
    Mar 17, 2009
    Messages:
    11,213
    Likes:
    569
    Location:
    AZ 86334
    Around here, retired wall-warts are available at charity thrift shops and yard sales... I have a box full that I keep around for projects...

    Do you need all three voltages all of the time?

    From what I remember of the older re-programmable micros, you do not need much current at 14.5 or 12.5V, so a simple shunt Zener is good enough.

    Maybe a high power 5Vdc source and an ebay step-up converter?
     
  3. mik3ca

    mik3ca Member

    Joined:
    Jun 24, 2017
    Messages:
    274
    Likes:
    1
    I need 5VDC for sure, and I can have either 12.5V or 14.5V along with it. (I don't need 12.5 and 14.5 at the same time)
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

    Joined:
    Oct 30, 2010
    Messages:
    9,997
    Likes:
    1,101
    ONLINE

    There is usually a VERY TIGHT tolerance on programming voltages including overshoot. On the system I used to program 2716 eproms, it was a linear regulator and a toggle switch. Vpp was off during start-up.
     
  6. mik3ca

    mik3ca Member

    Joined:
    Jun 24, 2017
    Messages:
    274
    Likes:
    1
    I misread it. Its 12V and 14V. So far, I found a voltage doubler made from 555 timer and a few diodes and capacitors, but using that on a 5V source would only give me 10V at best
     
  7. dknguyen

    dknguyen Well-Known Member

    Joined:
    May 6, 2006
    Messages:
    6,874
    Likes:
    82
    LTC1263 is made for this.
     
  8. MikeMl

    MikeMl Well-Known Member Most Helpful Member

    Joined:
    Mar 17, 2009
    Messages:
    11,213
    Likes:
    569
    Location:
    AZ 86334
    How about one of these?
     
  9. mik3ca

    mik3ca Member

    Joined:
    Jun 24, 2017
    Messages:
    274
    Likes:
    1
    I'm trying to avoid ordering extra pieces online if I can. I mean couldn't I make one from discrete parts I have on hand like diodes, capacitors, transistors and/or op-amps? and that LTC part that was mentioned claims it can do 12V from 5V not 14V.

    The parts I have almost immediate access to are also available online at this site: https://secure.sayal.com/STORE/index.asp

    As for the rest of the parts, I can see me either paying extreme shipping fees or I wait 21+ days for delivery.
     
  10. MikeMl

    MikeMl Well-Known Member Most Helpful Member

    Joined:
    Mar 17, 2009
    Messages:
    11,213
    Likes:
    569
    Location:
    AZ 86334
    Sayal carries LM317s in a TO-92, use one each for 12V and 14V. Start with an un-regulated 16 to 20Vdc wall-wart.

    Sayal carries regulated 5Vdc wall-warts...
     
  11. mik3ca

    mik3ca Member

    Joined:
    Jun 24, 2017
    Messages:
    274
    Likes:
    1
    I have a 6VDC wall wart I bought from them. I did make the "Blowit" programmer for the at89C2051 and it uses a resistor network and transistors to switch between 5 and 12V. Could I get away with it if I used 6V, made a voltage tripler then use resistor divider networks from its output to produce 14 and 12V? I tried LM317 regulators in the past and didnt like them.

    The blowit programmer details are here: http://www.oocities.org/dinceraydin/8051/index.html and the schematic is below.
    [​IMG]
     
  12. MikeMl

    MikeMl Well-Known Member Most Helpful Member

    Joined:
    Mar 17, 2009
    Messages:
    11,213
    Likes:
    569
    Location:
    AZ 86334
    Are you trying to use 6V on the AT89C2051?
     
  13. MikeMl

    MikeMl Well-Known Member Most Helpful Member

    Joined:
    Mar 17, 2009
    Messages:
    11,213
    Likes:
    569
    Location:
    AZ 86334
    Why not! What is not to like?
     
  14. mik3ca

    mik3ca Member

    Joined:
    Jun 24, 2017
    Messages:
    274
    Likes:
    1
    LM317 needs very accurate resistors for very accurate voltages. and for the at89c2051 I have 12V and 5V supply for it. What I'd like to do is use just one power supply for this new programmer for the w77e58 IC, so somehow I need a circuit that produces 5, 12, and 14V. and I'll never use the 12 and 14V at the same time.
     
  15. MikeMl

    MikeMl Well-Known Member Most Helpful Member

    Joined:
    Mar 17, 2009
    Messages:
    11,213
    Likes:
    569
    Location:
    AZ 86334
    so make one or the other variable, as in a pot. I usually set the lower resistor to 100 or 220Ω, then calculate the upper resistor. I choose an upper resistor which is about 10% low, and then make up the difference with a pot...
     
  16. mik3ca

    mik3ca Member

    Joined:
    Jun 24, 2017
    Messages:
    274
    Likes:
    1
    I came up with the following circuit to help with my issue. I'll use an 18V adapter, step it down to 15V then use one regulator to power other circuit parts with dedicated 5V. Then I'll use a simple transistor network shown below to select the voltage I want. Only issue I have is that if no transistor is selected (by making any base a logic high), then the output will be 15V which might destroy the chip since its highest recommended voltage for VPP is 14 for erase operations. I guess I'll have to do alot of number crunching unless theres an easier solution. Heck, ultimately, I want to make the 12v and 14v selections exclusive so I'm wondering if PNP transistors will help here.

    circuit.png
     

Share This Page