The LM LM series are monolithic frequency to voltage converters with a high gain op amp comparator de- signed to operate a relay lamp or other load. uses a charge pump technique and offers frequency doubling for low ripple, full input protection in two versions (LM,. LM) and its. The LM, LM series are monolithic frequency to voltage converters with a high gain op Details, datasheet, quote on part number: LM

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Dafasheet a hand-waving explanation from a digital and software guy who has bumped in to sharp edges in the analog side If I pulse 14V onto the “Signal In” port with that powersupply also connected to ground I think the problem is my Internal Zener references.

Read towards the bottom of lm29917 8 on the data sheet. Ideally, you’re going to need 8 pulses per second minimum, would be better for test purposes. I’m trying to make a frequency-to-voltage converter by using LM Sign up using Facebook.

Problem with LM Tach Circuit – 14 Pin version

You want it to keep dataseet measurements stable. You have fixed Pin 11 at about 0. The first op-amp is a camparator as your question states. An example circuit from the datasheet. Sign up using Email and Password. I’ve played around with a few variations.


What is the function of the second opamp? How are you pulsing the 14V?

C41 is a filter capacitor to reduce the ripple from the dagasheet pump. Once it stops raining here, I’ll drag it out and put it onto the bikes injector input at least and see if that makes it behave better The sig-in line goes from 5.

National Semiconductor

Sign up or log in Sign up using Daatsheet. Yeah – I figured that i needed a decent ‘frequency’ Since the chip was originally built to post-process a magnetic pickup for tachometer applications, the zero crossing would be easy to arrange for by directly wiring the pickup coil across pins 1 and 8.

I feel well past my depth trying to sort this out R46 is acting as a load for the charged signal. To help save hands, I hooked an LED up to the output signal. By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject datzsheet these policies.


The load is datasheft to convert the stored charge into a voltage that can be sensed, and pragmatically to provide a place for the stored charge to leak off into datasheet frequency falls. Andy aka k 10 The charge pump is charging a capacitor which one? I understand that, the input opamp works as a comparator and converts the sinusoidal signal into digital pulses. Email Required, but never shown.

How do I choose value of C41 I put a random one for now? That chip is made to detect RPM, most engines Idle rpm-ish, dataaheet you’re going to need a bunch of pulses or it’s going to measure 0. I then have another supply, also grounded to the common ground, thats 14V.

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I’m guessing the AC input is required to be centered on 0V, incidentally, but a DC blocking cap outside the chip would easily achieve that.