LM2907-8n to LM2917-14n for tachometer

[fever16]

lm2917

hello sir,
i have been working on the LED tachometer for my motorcycle which uses F-V converter.in that serach i found a german site. **broken link removed**
the ckt ( http://www.fda-technology.de/images/pic_Schaltplan 1_5.gif ) in that site uses LM2907-8pin version for F-V conversion.where as i already have LM2917-14 pin in my hand.i don't want to waste those chips.so can u help me in modifying the ckt.
this is my ckt.i want to drive just 10 LED's.all i need is replacing the LM2907 with LM2917
help pls
**broken link removed**

 

[polymath]

lm2917 tachometer

Hi fever16

Refer to National data sheet on the LM2907-LM2917
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Using the LM2917-14 in place of the LM2907-8

2907(8) pin no.      2917(14) pin no.
   1                  1
   2                  2
   3               3 & 4
   4                  5
   5                  8
   6                  9
   7                 10
   8              11 & 12

What the LM2575 regulator output voltage? If it is more than 7.5v you will need a resistor in series with pin9 of the LM2917(14) to use the internal zener - a value of 470Ω should work ok - check data sheet for required value.

hope this helps ... Polymath

 

[fever16]

lm2907-8n

thanks a lot polymath.
that LM2575 regulator output voltage is 5volts only i think.as it is mantioned as LM 2575 T5,0(fixed at 5.0).thats why i used 7805(easy to get and cheap)
i modified the ckt as u said pls have a look
**broken link removed**

 

[polymath]

lm2907 tachometer

Hi fever16

Your circuit looks ok.

You might consider including the reverse protection diode D44 as in the original.

Placing a suitable Varistor (20~30v) from D44/7805 node to Gnd would kill any spikes that may occur on the supply and damage the 7805.

regards ... Polymath

 

[fever16]

lm2917 circuit

thanks i'll place one.
regarding the ckt,is it ok to place R7,R8,R9 1K resistors.
and what is the function of P1 and P2

 

[polymath]

lm2907

Hi fever16

Please make some effort yourself!
READ the data sheet on the LM3914. Your answers are in it!
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The voltage at Pin6 is High end of comparator reference - it sets the Input Level to No.of LEDs lit.

The current out of Pin7 sets LED current - (brightness).

regards ... Polymath