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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LM Datasheet(PDF) – National Semiconductor (TI)

It just gives several example datssheet and a formula for the output voltage. I think you problem lies with the input circuitry of the LM The sig-in line goes from dtasheet. Here’s a hand-waving explanation from a digital and software guy who has bumped in to sharp edges in the analog side Sign up using Email and Password. I’m trying to make a frequency-to-voltage converter by using LM What is the function of the second opamp?

By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The load is needed 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 as frequency falls. The datasheet indicates a typical use case for the chip being to light a warning light when input frequency exceeds a threshold, in which case having an output transistor capable of sourcing or sinking more current makes sense.


Problem with LM Tach Circuit – 14 Pin version

That chip is made to detect RPM, most engines Idle rpm-ish, so you’re going datasheft need a bunch of pulses or it’s going to measure 0. This is confusing too.

datashset Page 1 of the data sheet says it all. I have then used the datasheet as well as this schematic to convert to 14 pin 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 to these policies.

Yeah – I figured that i needed a decent ‘frequency’ However you have no DC biasing ln2917 Pin 1 so it will just swing about with the AC coupled input and not do anything.

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.

I’ve built this on a breadboard using a modified version of http: I’ve played around with a few variations. You have fixed Pin 11 at about 0.


I’m stuck with a pin LM – i’ve got an dahasheet on order now, but damn it, I want to get this to work.

Read towards the bottom of page 8 on the data sheet. R46 is acting as a load for the charged signal. RBerteig 6 The first op-amp is a camparator as your question states.

Email Required, but never shown. Can anyone offer some guidance? To help save hands, I hooked an LED up to the output signal.

National Semiconductor

An example circuit from the datasheet. The charge pump is charging a capacitor which one? The LM’s datasheet is at http: I understand that, the input opamp works as a comparator and converts the sinusoidal signal into digital pulses.

Ideally, you’re going to need 8 pulses per second minimum, would be better for test purposes.

Its driving me nuts Sign up using Facebook.