reischle edited this page Apr 11, 2013 · 44 revisions

Apr 11 22:02 - The new digital storage oscilloscope makes life a lot easier. The quick measure feature keeps track of the servo pulse duty cycles and frequency. That is WAY better than on the old analog scope.

Duty cycle

Jan 04 22:23 - The servos' power requirement is amazingly high. While the quiescent current of the servos is at 9mA, it can peak to about 750mA. So a a USB power supply should be rated at 5V/1A.

Peak current

2013 Jan 01 22:15 - Released version with smoother servo movenment to resolve Issue #6

Dec 29 00:05 - Did some cleanup and released the new version with automatic bandwidth detection. Also restructured the main loop in preparation of averaging the meter movements.(Open issue #6)

Dec 21 01:40 - Dynamic bandwidth detection and scaling now working in the development branch.

Dec 14 22:25 - Noticed that the program gets stuck after one iteration due to a slight difference in the ethernet.begin() function that apparently came with version 1.0.1 of the Arduino IDE. Fixed that and uploaded a maintenance release.

June 25 12:00 - Assuming that in most cases the FritzBox will be the default gateway, I read its IP from the DHCP configuration. Cleaned up the code a bit which made the hex file considerably smaller.

Apr 1 17:00 - Changed the design over the weekend. The meter now resembles a dual moving coil meter. Built everything into a 10cm diameter Bratwurst tin can. Reversed the position of one servo in the sketch. Uploaded new scale.pdf. Pic of the new design: voltage dropping

Mar 30 06:45 - Put some pin12 hi/lo commands in toggle the UNO's onboard LED to see if the program is running.

Mar 29 13:15 - It seems others have suffered from interference from SG90 servos as well: See comment on this video The Fritzmeter has been running for more that 10 hours without crashing. Probably due to the softReset function.

Mar 29 01:30h - Added softReset() function to kick in when connection to Fritzbox fails. This is neither supported nor recommended. I'll have to see how it works.

Mar 29 00:30h - Fixed my bench power supply. Things look way better now. Still the PSU output voltage drops by 2V when both servos are moving.

voltage dropping Y setting is 3V/div. servopulse

Left pic: Voltage in bench PSU drops significantly when servos are moving. - Right pic: Servopulse looks OK.

At least they can't throw off the micro controller (USB powered) any more. For some reason the frequency counter reads 50Hz on one the servo and 150Hz on the other servo's control line. Checking with the Oscilloscope shows no difference between the two signals. Can't spot what triggers the counter.

Mar 28 13:00h - Used bench power supply for servos. Both servos went totally haywire. The servo sweep example sketch worked ok. I'm ovbiously missing something. Started further analysis: Frequency counter showed servo pulse at 50Hz, so that's ok. Will need to check with scope and see if I can spot the difference between my sketch and the servo sweep example.

Mar 28 7:00h - Reading the router address fron the dhcp client is fairly simple. Will implement ASAP

Mar 23 21:40h - Noticed that one of the servos from time to time emitted a low hum. The Oscilloscope showed the Arduino's 5V rail droping by 0.5V. Further investigation showed that when both servos moved rapidly, Vcc sometimes dropped by up to 2V. This totally threw the servos off balance which caused them to move fantically. This behaviour takes a few seconds to settle. - Either one of the servos is out of its specs or I need an external power source to drive the servos. This is directly related to issue #2 in the tracker.

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