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Comment Wall (3 comments)

At 5:29pm on September 21, 2009,
William Premerlani

I am going to continue our dialog on your servos here for a while.

Since the HiTech servo worked with the board, the board must be ok.

I assume that you checked the servos with the radio. I am sure they work, but I suggest you double check to be sure. We better not assume anything at this point.

I suggest you put the PWM period back to 25000 before we forget. Once things get running, that is where we will want it.

It would help me if you could find the actual technical spec for the servos and for the radio that you actually have. I am not sure if I believe the spec you pointed me to.

Finally, it would help if you could check the polarity of the pulses coming out of your radio. An oscilloscope would be best to take a look, but if you don't have one, a meter will work. Measure the signal with respect to ground.

If the pulses are normal polarity, mostly the meter will read low, with occasional jumps to 5 volts.

If the pulses are reversed polarity, mostly the meter will read close to 5 volts, with occasional jumps down to 0.

In any case, tell me what the meter reads.

Anyway, I am signing off for tonight, I will sleep on it, maybe I will have more ideas tomorrow.

Sorry that this is taking so long.

By the way, it is most likely that the servos you have and your radio are not based on the types of pulses the board is expecting. So in the end, we are either going to have to modify the firmware, are you are going to get find a radio and servos that are compatible with the board.

I would like to eventually have the firmware work with any radio and servos, so sooner or later I will likely bring the firmware in line with your equipment, but it is going to take a while.

Best regards,
At 5:55pm on September 21, 2009,
William Premerlani

Before I sign off for the night....

The problem is most certainly a pulse definition compatibility issue. It can only be a couple of things at this point:

1. Pulse polarity. If this is the case, it would not be too hard to fix it. As a matter of fact, I think that Ben Levitt has already provided for this option in his version of the firmware, which we have not tested yet.

2. The ordering of the three wires in the cable. I thought that all servos use the same ordering, but I could be wrong. I thought it was always ground, +, and signal. Just to be sure, measure the voltages on the three pins coming out of your receiver, see if this is the case. The other day you mentioned that you were seeing 3.2 volts on the power bus of the board. That surprised me, it seemed low. Possibly it came out that way because your transmitter/Rx uses a different signal sequence.

Best regards,
At 7:22pm on September 21, 2009,
William Premerlani
Hi Justin,

Well, I am relieved that you finally figured it out. Good for you.

Before you use John's firmware, please get in contact with him to make sure that you have the latest version, that you know how to set it up and operate it. Send John a message, I am sure he will get back to you.

I have been helping him develop it, so I know a little bit about it.

There are a couple of parameters that you need to set that have to do with the slight pitch and roll angles that a helicopter assumes in a hover to counteract some unbalanced forces. John can tell you more about them. If you do not set them, your heli will fly level, but that will lead to lateral translation. Basically, the tail rotor acts like a propeller. John and I also realized that there is a pitch force as well.

You also need to set some feedback gains, and a "boost gain" so that your controls can continue to feel "lively". The stabilization tends to make it sluggish.

Also, I forgot which board you said you have. If you have a green board, there are no worries, just mount the board and use John's firmware.

However, if you have a red board, there are two things you will need to do:

1. Select the red board firmware configuration. It is not hard to do, but it does have to be done. Let me know when you get John's files, I will tell you what line to change.

2. Provide vibration isolation. The LISY gyros on the red board are disrupted by the vibrations that a heli generates.

Best regards,

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