Author Topic: how to get a waveform to show up on a screen?  (Read 743 times)

0 Members and 1 Guest are viewing this topic.

Offline DmeadsTopic starter

  • Regular Contributor
  • *
  • Posts: 171
  • Country: us
  • who needs deep learning when you have 555 timers
how to get a waveform to show up on a screen?
« on: May 11, 2019, 07:40:07 am »
Hey!

I am trying to build a heart rate monitor, and I want to be able to see the output waveform on a little lcd or OLED screen.

Does anyone know how to do this? Is there like a mini oscilloscope that does this? the signal isn't that large like 7 volts probably, so I wouldnt need a giant screen.

Also are the screens high input impedence?
 

Offline radiolistener

  • Super Contributor
  • ***
  • Posts: 4135
  • Country: 00
Re: how to get a waveform to show up on a screen?
« Reply #1 on: May 11, 2019, 11:26:22 am »
7 V is a bit large for direct ADC input. So, you're need simple voltage divider before ADC input. Also it needs to add analog bandbass filter, to eliminate high frequency noises and pulses. Then you're need to capture ADC output at fixed sample rate and record it into memory. Then render it into video memory of LCD controller.

I think you will need memory for at least 10-30 seconds. Most likely 3-10 kHz sample rate will be enough for you to capture all details. With 10 kHz and 30 sec, you will need memory buffer for about 300 kilosamples.

Here is some application note, which may be useful to get started: https://www.nxp.com/docs/en/application-note/AN4059.pdf?&amp%3Btid=AMdlDR
« Last Edit: May 11, 2019, 11:30:00 am by radiolistener »
 

Offline DmeadsTopic starter

  • Regular Contributor
  • *
  • Posts: 171
  • Country: us
  • who needs deep learning when you have 555 timers
Re: how to get a waveform to show up on a screen?
« Reply #2 on: May 13, 2019, 10:09:53 pm »
thanks!!!
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf