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by hojo
Thu Jul 18, 2019 5:17 pm
Forum: Networking and servers
Topic: RadioHead LoRa library freezing the Raspberry
Replies: 10
Views: 2663

Re: RadioHead LoRa library freezing the Raspberry

I just fixed the rf95_client.cpp to use the _lev instead of _ren and it worked. If you are using bcm2835_gpio_ren() to detect interrupts your system will hang. Use bcm2835_gpio_lev() instead. Is there any reference to this that we could see to know why _ren fails? I presume, at some point in time, i...
by hojo
Tue Jul 02, 2019 9:32 pm
Forum: Camera board
Topic: v2 camera can capture 1000fps videos ...
Replies: 35
Views: 13481

Re: v2 camera can capture 1000fps videos ...

Sweet. I'll have to look at that. This gives me a place to start as cameras and video are not my forte in any way. In short, my goal is to build a system for race timing where the camera acts as a backup timer. Any issues with times and we can go back to the video and see who cross the finish line, ...
by hojo
Sun Jun 30, 2019 10:32 pm
Forum: Camera board
Topic: v2 camera can capture 1000fps videos ...
Replies: 35
Views: 13481

Re: v2 camera can capture 1000fps videos ...

This is all very exciting. I just spent quite some time looking for the I2C information for GoPro, wanting to figure out how to inject my own time code (there is an existing solution one can buy, of course). But, since my solution doesn't need gopro or even that high of resolution (and the time code...
by hojo
Fri Jan 12, 2018 8:19 pm
Forum: Compute Module
Topic: 3G/4G/LTE modem for CM3 and I/O board
Replies: 4
Views: 22965

Re: 3G/4G/LTE modem for CM3 and I/O board

I am also searching for this functionality. Adafruit sells these ones: https://www.adafruit.com/?q=cellular and I just found this one as well https://www.robotshop.com/en/micro-quad-band-gsm-shield-arduino-raspberry-pi.html?gclid=EAIaIQobChMIgJ-u74HT2AIVh7fACh0NmwbHEAQYBSABEgLO4fD_BwE. If there are ...
by hojo
Sun May 15, 2016 8:59 pm
Forum: Networking and servers
Topic: Options for GPS/PPS/NTP server
Replies: 1
Views: 1776

Options for GPS/PPS/NTP server

I'm building two time servers for use as start/stop timers in remote river (kayak/raft) racing. I decided to use GPS disciplined clocks as I will be absolutely off the grid for the majority of races. I've been following a few different howtos and pouring over the various user groups. Here are the th...
by hojo
Wed Apr 27, 2016 3:07 pm
Forum: General discussion
Topic: Car Horn Relay Calculations
Replies: 10
Views: 1834

Re: Car Horn Relay Calculations

Gentleman, I'm happy to report that the circuit design concerning the transistor/relay trigger is an unqualified success! I must again give thanks! I am unhappy to report that despite my computer PS stating that it provides 12v/14a, a single horn hit drains the power to dip the 5v rail powering the ...
by hojo
Wed Apr 20, 2016 2:48 pm
Forum: General discussion
Topic: Car Horn Relay Calculations
Replies: 10
Views: 1834

Re: Car Horn Relay Calculations

The max was more of an academic exercise, just to see if I could calculate the resistor for tie PI with the 8A limit of the TIP102. From what I can tell, each horn is really around 3ohms (I measured it today). I guess the 8A does fit the listed max though I'm not interested in trying to max out any ...
by hojo
Wed Apr 20, 2016 2:54 am
Forum: General discussion
Topic: Car Horn Relay Calculations
Replies: 10
Views: 1834

Re: Car Horn Relay Calculations

Mark and David, I think I'm catching on. First (3.3V-1.4V)/1k Ohm = 2.9 Did you did the math for 2.8/1k rather than 1.9/1k which would be 1.9mA. I'm presuming that this is enough to drive the transistor. The link I used states that Ib = Ic/hFE and the example is actually quite close to the original....
by hojo
Tue Apr 19, 2016 9:03 pm
Forum: General discussion
Topic: Car Horn Relay Calculations
Replies: 10
Views: 1834

Re: Car Horn Relay Calculations

Mark, thanks for your feedback! To reiterate for my benefit, the hFE numbers are load limits. Since my load is under the 3A, I use 1000. If, say, I wasn't using the relay and trying to switch a single horn using the transistor alone then that load (~6A) would stipulate that I use the hFE of 200. You...
by hojo
Tue Apr 19, 2016 7:28 pm
Forum: General discussion
Topic: Car Horn Relay Calculations
Replies: 10
Views: 1834

Re: Car Horn Relay Calculations

I found this online tool, though I'm still not clear on which hFE values to use: http://www.petervis.com/GCSE_Design_and_Technology_Electronic_Products/transistor_base_resistor_calculator/transistor_base_resistor_calculator.html I filled it out with these values for the TIP102: Vbe = 2.8 Vce = 2.0 h...
by hojo
Mon Apr 18, 2016 5:09 pm
Forum: General discussion
Topic: Car Horn Relay Calculations
Replies: 10
Views: 1834

Car Horn Relay Calculations

Greetings! I’d very much appreciate any help in building this circuit. It’s the horn segment of a countdown timer for a kayaking competition (I need it loud because it’s used in a river setting, hence the car horns). My circuit: Screen Shot 2016-04-18 at 10.58.26 AM.png I based my design on these tw...

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