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Lm340T5 instead of LM340H5

  1. Jan 12, 2013 #1
    Hey all,
    Im working on making a signal converter for a mod ive done on my car,

    the plans for it are from zilvia.net - 164351-s15-cluster-sig-converter (edit: link was not working and apparently triggered spam detector)

    yet ive been looking around alot of places and cant find the lm340H-5 and lm340H-12 (or the lm140 it says could be used instead)

    I have however found a place i can get lm340T-5 and lm340T-12

    what im wondering is can i use those regulators instead of the ones the schematics asks for?



    ive copyed the info from the other thread that the link wont work to below
    Here is the part list:

    Part Value

    C1 0.01U
    C2 0.01U
    C2A 1U
    C2B 1U
    C3 0.1U
    C4 1U
    C5 0.1U
    C6 0.22U
    C7 0.22U
    C8 0.1U
    C9 0.1U
    IC1 LM340H-05 or LM140A-05
    IC2 LM340H-12 or LM140A-12

    IC3 74LS109N
    IC4 LM331N
    IC5 LM2917
    R1 100K
    R2 10K
    R3 100K
    R4 470
    R5 100K
    R6 47
    R7 6.8K
    R8 10K
    R9 6.8K
    R10 5K

    All resistors are 5% or less and all the caps are ceramic or tantalum.
    This is needed to keep the temp coef down. It can get hot under the dash.

    Now lets get into what everything does.

    -Power and logic levels-

    IC1 and IC2 are the volatge regulators. IC2, C7 and C8 regulate the input voltage
    to 12v which is used for power to the LM2917 and LM331. IC1,C6 and C5 then regulate
    that to 5v for logic high and power for the 74LS109N.

    -Input frequency to voltage converter-

    IC5, R1, R2, R4, C9, C1, C2A, C2B are used to convert the speedo input from a
    zero crossing signwave to a voltage.

    C9 is a filter for the input since its really noisy. R4 is for voltage dropping
    sice the LM2917 has a 7.6v internal zener regulator.

    The output voltage is defined by Vout = Vcc * Fin * C1 * R1 * K
    where K = 1 and VCC = 7.6

    The output ripple is defined by Vripp = (Vcc / 2) * (C1/(C2A+C2B)) * (1 - ((Vcc * Fin * C1) / I3))
    where VCC = 7.6, I3 = 180uA, Fin = input freq 4.5hz(1mph) - 810hz(180mph)

    -Voltage to frequency converter primary-

    IC4, R3, C3, C4, R5, R6, R7, C2, R9, R10 are used to convert the voltage back to a frequency.
    That frequency is defined by Fout = (Vin/2.09) * ((R9+R10)/R5) * (1/ (R7 * C2))
    Where Vin = Vout from the F-to-V converter.

    R10 is adjustable so the conversion factor can be fully adjusted.

    R6 and C4 are used to keep the internal referance stable.
    R3 and C3 are for input filtering.

    -Signal conditioning-

    IC3 and R8 are used to form the 50% duty cycle square wave. IC3 is a dual J/K
    flip flop so the output will change its state once per pulse and dividing the
    primary output freq by 2. This is needed because the output pulse width from the LM331
    is too small.

    Output here should be 12.5hz/mph
    Last edited: Jan 12, 2013
  2. jcsd
  3. Jan 12, 2013 #2


    User Avatar
    Science Advisor
    Homework Helper

    The H and T are probably different styles of packages for the same electronic device.

    H is probably a TO39, round package with 3 pins from the base. T is probably a flat T0220 package designed for bolting onto a heatsink.

    Since your circuit seems to be very low power, you probably don't need a heatsink anyway so it doesn't matter which you use, but if you have a circuit board, it will be designed to take one or the other, and the T package is bigger than the H.

    FWIW the commonest parts used now for these regulators are the 7805 and 7812 which you can get anywhere - unless there some reason why you really need the 340 parts for this circuit.
  4. Jan 12, 2013 #3
    thanks for the quick reply,
    turns out in the jaycar catalouge the 7805 and 7812 are listed as 7805/lm340t5 so thats good, im going to try them out,

    found another issue though,

    chip lm2917 i have one and its a 14 pin chip, the one the person who made the above used was a 8 pin chip, if i use the 14 pin chip do i still just use the same pin numbers or will it be a different layout ?

    thanks again

    edit: looking at the data sheets i need to bridge pin 11 and 12, then bridge pin 3 and 4, and then i should pretty much have the same chip and just use the data sheet to see what pins do what?
    Last edited: Jan 12, 2013
  5. Jan 13, 2013 #4


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    Science Advisor
    Homework Helper

    That looks about right. Figures 2 and 4 on http://www.ti.com/lit/ds/symlink/lm2917-n.pdf
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