Hi all,

I'm a bit of a newb I'm afraid, apologies in advance.

I've decided I'd like to make a shift light for my motorbike, and from some googling I decided a National Semiconductor LM2917 would be the way to go about this.

http://www.national.com/pf/LM/LM2917.html

Anyway I have Multisim 9 (I thought this would be handy as I should be able to figure out my circuit before I waste the money) and wondered if anyone had this component so I can add it to my db. I've tried the wizard to create one, but it's a little bit beyond me at the moment.

Is there an online repository for said components please?

Thank you for your time,

Russ

 

Doesnt look like National makes a model for this. If you are worried about your circuit working, post it up here for everyone to review.

 

Optikon: Ok thank you.

Thanks for the offer. I'd really like to simulate this in Multisim though as I'm a bit of a newbie and I could be posting a fair few times before I even come close. Also I figured it'd help with teaching myself? I may have the wrong idea with multisim though.

Thanks

 

The output from the LM2917 is a pretty straight forward voltage directly related to the RPM, so all you need to simulate it is a voltage source in multisim. You'll have a problem on the real device as the chip needs 15 volts, aren't most motorcycles 6 or 12 volt systems? So you'll have to have a switch mode or boost converter to power it.

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You cannot really "learn" from a simulator. You have to understand that the simulator is a verification tool. You must first design your circuit and understand how it works before you simulate. If you do not take on this philosphy, you will believe everything that the simulator tells you and have much trouble in your life (because the simulator is only as good as the modelling which is far from perfect)

It is somewhat of an art to understand what issues are related to poor modelling and which are real design problems. If you are new to this, I would suggest first designing your circuit on paper and then having other people look it over for problems. After you have a complete understanding of the operation & theory, then you can try to model it in a simulator and see if the results match what you expect. If they don't, then understand why not. Once you have mastered the differences (if any) and all is working well then you are ready to build it and try it out. After you build it, you will then likely find things that do not match your modelling nor your theory and you should strive to understand why. Some things are just too hard to model and too complex to understand theoretically so start of with some very easy projects!

 

I disagree with Optikon in that you can learn tons from a simulator, but he's right, you can't design a real world circuit in it from scratch without at least some idea beforehand of how the real world components compare. Simulated components are almost always ideal, and nothing in the real world is ideal, and it takes quiet a while to learn where to put parasitic components in a simulation to make it model a real world system more closely.

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I agree with Optikon but when you are ready to simulate, I have a spice model of LM2907 (same device, without the internal zener). Check out http://www.geocities.com/russlk/LM2907.txt
You may have to copy and paste the URL, Geocities is funny that way.
The URL is not working, so email me for a copy.

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see my website: www.geocities.com/russlk

 

Thanks for the advice guys, and the heads up on the 15v (doh).

I'm a programmer by trade so I'm very aware that I'll need to understand it first, would be like guessing and programming and hoping it compiles...

Just thought it'd be a useful tool to assist with teaching myself I'll be sure to post up my ideas (as and when I get started).

Russlk: I will e-mail you soon as I'm home, thank you

 

 

I was planning on using this IC for an automotive application... I was curious to see the post (3rd) saying it required a 15V supply... Is this really true? From the data sheet, there are two examples with 12V service? Could this be an oversight or am I missing something? Thanks!

 

The LM2917 has an internal 7.5 volt zener, so it will work down that low. You have to have a series resistor to limit the current or the zener will burn up, see the data sheet.

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see my website: www.geocities.com/russlk

 

Russlk,

Thanks for the post! Also, thanks for the spice model, I'm putting together a virtual circuit to simulate so it will come in useful! Just found this forum - Wow!

 

Do you know if this spice model works with OrCad's pSpice?

 

The datasheet has the circuit for "a shift light".

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Uncle $crooge

 

I believe that it will, the LM2907 model is standard Spice and I think Pspice supports that.

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see my website: www.geocities.com/russlk