/technologies/sensor-technology/b/blog/posts/rohm-heart-rate-optical-sensor-bh1790glcI was Road Testing the Rohm SensorShield-EVK-003 (Arduino Compatible) and the sensors that come with it, in 2017.One of the sensors that I hadn&#39;t reviewed during the test, is the BH1790GLC Heart Rate Monitor.I&#39;m going to use tha...en-USTelligent Community 12https://community.element14.com/technologies/sensor-technology/b/blog/posts/rohm-heart-rate-optical-sensor-bh1790glcThu, 20 Jan 2022 21:35:57 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:16db3fbb-213a-4eca-9078-eb0d04c82dceJan Cumps0<p>Scope captures of the two LED cathodes. The IC works as a pull-down open collector. Led is on when the value is low.<br />The device is actually a controlled current source, but&nbsp;we can interpret the voltage like that.</p> <p>The pulse wave trains&nbsp;frequency is 32 kHz. That matches the sketch timer. All pulse trains look similar.</p> <p><img src="/resized-image/__size/1280x720/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-16db3fbb-213a-4eca-9078-eb0d04c82dce/pastedimage1642713009936v1.png" alt=" " /></p> <p></p> <p>They have a start pulse and then 4 sequenced pulses. The time between start and first sequenced pulse is 30.8 ms. I didn&#39;t find that back in the datasheet.</p> <p><img src="/resized-image/__size/1280x720/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-16db3fbb-213a-4eca-9078-eb0d04c82dce/pastedimage1642713090487v3.png" alt=" " /></p> <p></p> <p>4 sequenced pulses are at 242 Hz. I don&#39;t know where that&#39;s coming from.<br />According to the datasheet, this can either be 64 or 128 Hz. I made&nbsp;the measurements with higher sample rates but always ended around the 242 Hz frequency.</p> <p><img src="/resized-image/__size/1280x720/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-16db3fbb-213a-4eca-9078-eb0d04c82dce/pastedimage1642713052697v2.png" alt=" " /></p> <p></p> <p>Led on time is 0.3 ms. That corresponds with one of the two valid settings in the datasheet:</p> <p><img src="/resized-image/__size/1280x720/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-16db3fbb-213a-4eca-9078-eb0d04c82dce/pastedimage1642713711727v4.png" alt=" " /></p> <p></p><img src="https://community.element14.com/aggbug?PostID=22791&AppID=17&AppType=Weblog&ContentType=0" width="1" height="1">