Creating a sine and triangle reference wave from analog stuff - Page 1
Forum section: electronics / beginners

author: Belrmar
author_rank: Regular Contributor
timestamp: June 26, 2017, 08:00:43 pm
content: i am planinng on creating my own sinusoidal wave inverter, but i need a reference, i know i could use a microcontroller with a dac, but thats the easy way haha

author: Benta
author_rank: Super Contributor
timestamp: June 26, 2017, 08:05:38 pm
content: Check out Intersil ICL8038 and Exar XR2206.Ancient devices, but the principle works.

author: Zero999
author_rank: Super Contributor
timestamp: June 26, 2017, 09:20:09 pm
content: Unfortunately both the Intersil ICL8038 and Exar XR2206 stop being made years ago. Luckily there are plenty of clones and old parts still available.There are various ways to implement this with standard components. First, make a triangle wave with an integrator and comparator, then convert it to a sine wave using a non-linear network.https://www.eevblog.com/forum/beginners/simple-analog-function-generator-design/msg1174983/#msg1174983https://www.eevblog.com/forum/projects/function-generator-ics/msg66399/#msg66399

author: danadak
author_rank: Super Contributor
timestamp: June 26, 2017, 10:56:50 pm
content: Here is an approach using a quad OpAmp -http://www.instructables.com/id/THE-SIMPLEST-FUNCTION-GENERATOR-BUILT-ON-A-BREADBO/Regards, Dana.

author: danadak
author_rank: Super Contributor
timestamp: June 26, 2017, 10:59:10 pm
content: Here is a method using PSOC, results in lot better precision,and easy to control under code.http://www.cypress.com/documentation/application-notes/an69133-psoc-3-psoc-5lp-easy-waveform-generation-wavedac8-componentRegards, Dana.

author: shteii01
author_rank: Frequent Contributor
timestamp: June 27, 2017, 12:00:15 am
content: what frequency?

author: danadak
author_rank: Super Contributor
timestamp: June 27, 2017, 12:52:04 am
content: I assume you are referring to the PSOC approach. Take a look at ap note,this is a table driven DDS design, so you trade off table size vs upperlimit freq.For example, a table size of 32, current mode, result is 6 Mhz / 32 =~ 187 Khz.http://www.cypress.com/documentation/application-notes/an69133-psoc-3-psoc-5lp-easy-waveform-generation-wavedac8-componentRegards, Dana.

author: mikerj
author_rank: Super Contributor
timestamp: June 27, 2017, 07:32:26 pm
content: Quote from: Belrmar on June 26, 2017, 08:00:43 pmGenerating a sinusoid through analog means and then stepping it up with a transformer (which is what is sounds like you mean) would make an inverter with terrible efficiency. The way sine inverters (usualy) work is to step up the voltage to the required peak value (e.g. 340v for UK/Australia) and then use high(ish) frequency PWM to switch an H bridge to generate the sine. Alternatively you could PWM an H bridge on the low voltage side of a transformer, so you'd be dealing with high currents instead of high voltages.Since you need PWM anyway, you might as well generate the sine with a micro that has a suitable PWM generator. You could do all this in analog, but it would be vastly more complex.

author: MrAl
author_rank: Super Contributor
timestamp: June 28, 2017, 01:09:25 pm
content: Hello there,I agree with the PWM suggestions but if you are going to generate PWM using an analog method then you probably are seeking to generate first a sine wave reference, then use a triangle wave compared with that sine wave to generate the PWM pulse widths. That gives you the proper pulse widths to drive the H bridge with. That's not my preferred way to do it, but if you are stuck in analog land then you may have less options that work as well as that one.To this end, it is easier to generate a sine wave with a sine wave oscillator. There are different kinds out there so you should look around and see if you can find one you like. You can get some very clean sines out of these things and at line frequencies it works pretty well even with cheap parts. If you intend to change frequency you'll have to give it some more thought.