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| From: | Prof. Dr.-Ing. Heinrich Warmers |
| Subject: | Re: [Paparazzi-devel] apogee board 2.0 - feature questions |
| Date: | Sat, 17 Oct 2015 10:22:14 +0200 |
| User-agent: | Mozilla/5.0 (Windows NT 5.0; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 |
Dear Jan,in the data sheet a current of 1.4 µA only for the 32Khz oscillator is given. To use a special chip on a small separate pcb connected via i2c is a better way.
Is there a chance to use a vibration resistance accelerator sensor chip like the MXR9500 as option? The use of this chip gives a better flight behaviour mentioned by the KroozSD- and Mikrocopter- autopilots.
In the first mikrocopter-autopilot only the z- axis is used by this sensor. http://wiki.mikrokopter.de/en/FlightCtrl_ME_2_2_ACC Is the coupling from the power circuit a mechanical or a electric problem? regards Heinrich Am 14.10.2015 20:23, schrieb Jan Čapek:
Hi, let me comment on this: Gautier was pointing out to eliminate the backup capacitor since the RTC could get synchronised from the GPS or from the ground station if no GPS is available. We have tested the gold cap setup on Apogee 1.0 and it doesn't seem to hold the RTC system backup for a very long time. It looks like the power is gone within 0.5-1hour after the system has been disconnected from the main power source. I would be interested in other people experience. Unfortunately, the STM datasheets don't seem to specify the expected current that is being drawn by the battery backup subsystem. We have tested the same goldcaps separately outside of the board and they retain their voltage for days. Removing the goldcap would give us some extra space to move the IMU further away from the switching power supply - thanks Gautier for this valuable input. Back to your question - the port has fully integrated RTC - external 32kHz oscillator and the system enables/uses the interal RTC subsystem. And it will do so even if the goldcap will get removed. Just the source for synchronizing the clock will either be GPS or the ground station. Jan On Wed, 14 Oct 2015 17:26:34 +0200 "Prof. Dr.-Ing. Heinrich Warmers"<address@hidden> wrote:Hi, is the port for the additional clock 32 kHz free ? If this is true you can use the inside RTC of the STM processor by adding a clock resonator, a gold cap a resistor and a diode. Heinrich Am 12.10.2015 22:23, schrieb Gautier Hattenberger:Hi, As a side note, I would suggest to remove the RTC backup capacitor to save some space on the board. The clock is set using the GPS time and the backup is used to set the time and date of log files. So having a backup is only needed if you fly without GPS not too long after having a GPS fix in a previous flight. Worse case, the date of your log file is wrong. Even this could be fixed with some messages from the ground station to have an approximate time. Gautier Le 12/10/2015 17:59, Jan Čapek a écrit :Hi, thank you for the feedback, please, see my further comments below On Mon, 12 Oct 2015 16:44:04 +0200 Michel GORRAZ<address@hidden> wrote:Hello Jan - IMU will be updated with MPU9250. This will eliminate need for anexternal magnetometerApogee v1.00 is MPU9150 compliant (it includes a _crappy_ mag) but using a MPU9250 is a good idea. If possible, put the 9250 as far as possible from the switching power supply.Good point here, too, not sure if there is space on the board for this to be moved. Let's see what we can do here.- SD card sold is discontinued, and will be replaced by the one currently in production by molexNew Molex ref is 503182-1853 (exact replacement of 503182-0853)Yup, this one will be used instead.- mounting holes - we find the 1.8mm holes pretty difficult for mounting the board. The holes will be changed to 2.5mmv1.00 holes are 2mm, if you really want to increase the diameter, use 3mm, easier to find than 2.5mmYou are right, however 3mm holes already seem to leave too little material on the edge of the PCB. We will consider that, too.- servo connectors - we would like to turn the 3 pin connectors 180 degrees, so that pin 1 corresponds with servos signal. This will make the board consistent with the standard molex 1.25->futaba/JR harness cables ( http://hobbyking.com/hobbyking/store/__46385__Male_Molex_1_25_to_Female_JR_Servo_Extension_1pc_EU_Warehouse_.html?strSearch=molex%201.25 )For some historical reasons, GND is always on pin 1 of all connectors, so doing this you will be hobbyking compliant but not pprz anymore (hello magic smoke) You better buy a tool to swap the hobbyking's harness molex pins : http://www.digikey.com/product-detail/en/0011030043/WM9937-ND/252489I am aware of this, swapping is not a problem. However, a regular user may not notice that reverse layout. Magic smoke won't happen in either case since the power+ is always in the middle, in the worst case you would just ground the servo signal. We will consider your objection.- power connector - we find the power connection to the board a bit difficult without a proper connector. The 4mm connectors (the distance between the 2 pads) are rather too big for such a tiny board. We will place a 4 pin 1.25mm molex blade header - pins 1,2 as Vdd+, and pins 3,4 as GND. This will still leave the option to solder wires directly to the board.TDon't forget the current of the entire aircraft (servos, modem, GPS...,) will go through your tiny 1.25mm Molex (0.8A max with 32AWG cable)...That is why we would use 2+2pins. Anyway, I will consider if there are other options for the connector.Good luck for routing ;-) Regards MichelThank you for all the valuable comments, Jan _______________________________________________ Paparazzi-devel mailing list address@hidden https://lists.nongnu.org/mailman/listinfo/paparazzi-devel_______________________________________________ Paparazzi-devel mailing list address@hidden https://lists.nongnu.org/mailman/listinfo/paparazzi-devel_______________________________________________ Paparazzi-devel mailing list address@hidden https://lists.nongnu.org/mailman/listinfo/paparazzi-devel_______________________________________________ Paparazzi-devel mailing list address@hidden https://lists.nongnu.org/mailman/listinfo/paparazzi-devel
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