PBP projects for R/C models

[mackrackit]

Darn,
I thought the SRF05 was the same thing as the PING. Now I see that the SRF05 takes a different trigger pulse.

So it looks like I just wasted your time on that part.

I guess on the good side rmteo noticed another possible problem.

I wonder if a While/Wend loop using PWM would be the answer?

[Kenjones1935]

Originally Posted by Kenjones1935 View Post
The Electronic Speed Control wants this PWM signal to arrive at 50 hz.

I was not clear in my last posting. The Electronic Speed Control PWM specification is for a single positive pulse no less than 1ms and no more than 2ms once per 20 ms, ie 50 pulses per second. The one to two millisecond pulse width is divided into 256 parts. 1.5 ms corresponds to 128 which corresponds to neutral in a servo.

Neutral is steering straight on a steering servo. Neutral is stopped on a wheel driving servo.

I discovered that using HPWM with the 4mhz default oscillator a pulse width of 100 to 110 gets the behavior of 'neutral' on my car. For example "HPWM 1, 100, 50" turns the front wheels of my car to straight. See the attached picture. Channel 2 is the HPWM version of neutral. Channel 3 is what the radio receiver sends.

Ken

[Kenjones1935]

I have found a way to make short, 10 to 80 usec pulses while using the 4mhz oscillator. The SRF05 proximity detector wants at least 10 usec. If I give it super long pulses catching the following echo measurement can be a problem for PULSIN.

Sooo the following makes an 80 usec positive pulse.

SYMBOL trigright = PORTB.0
LOW trigright
HIGH trigright
HIGH trigright
HIGH trigright
LOW trigright.

One thing at a time.

Ken

[Kenjones1935]

I now have the sonic ping devices (SRF05's) flashing continuously. There is no blockage in the PIC's processing.

Now the car is reacting too quickly. There is a bit of code that used to guarantee a 1/2 second backing up when backing up was necessary. Now the count down for this delay is instantaneous. While turning a corner the proximity sensor data gets confusing. Both the side sensors and the forward sensors are hearing important echos. I might need to adjust the positions of the two SRF05's or write some code especially for that situation. I am not sure - elusive. Like I said.


Ken

[Ioannis]

Hope you are not activating both sensors at the same time, right? Be sure to give some time for the echo to decline enough before confusses the other sensor.

Ioannis

[Kenjones1935]

I've added a PAUSE of 1/10sec between the front trigger and the side trigger. This noticeably slows down the flashing of the LEDs on the SRF05s. In the audible range I can easily hear echos in a room. I have no experience with ultra-sound in the range that the SRF05 emits. The spec shows a time line in which the pulses seem to be a square wave of 2usec cycles. That is a little burst of 500,000 cycles per second sound that appears to last about 20 usec.

This little project keeps gets interestinger and interestinger!

If there were five cars racing near each other on this gymnasium track, would their SRF05's get confused. I don't think so, but I am not sure....

Ken

[Ioannis]

If there were five cars racing near each other on this gymnasium track, would their SRF05's get confused. I don't think so, but I am not sure....

They SURE would. That is what I noted on my previous post. Your sensors are hearing echoes that keep coming long after the transmission stopped. No matter which of the SRF05's did the transmission. Keep note of that.

Maybe an IR sensor would be more appropriate here. Also faster.

Ioannis