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Old 02-26-2005, 01:52 AM   #31
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Default Re: Top Speeds

Quote:
Originally posted by nimble


Now I know some gas cars claim they can hit 60+mph, which at those speeds, these figures are doubled,
but how many tracks actually have cars going this fast?
Any place that does 1/8th scale. Pretty much any large outdoor roadcourse.



BTW...range would have to be WAY more than 120' for your system to be suitable for 1/8th scale.
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Old 02-27-2005, 04:31 PM   #32
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Quote:
Some simple math shows that each MPH in speed translates into a distance of .0176 inches each millisecond.
Something else to note. At 30mph, a car will travel 68 inches, or 5-1/2 feet in 128ms. With a fail-safe mode fixed at 128ms delay, almost 6-feet of travel before the brakes are applied.

I wonder why Spektrum has a 128ms value? If the car isn't getting any input after 16ms or 32ms, why wait 128ms before doing something about it?
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Old 03-04-2005, 06:12 PM   #33
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Default New Sportsman DC charger

Due to demand for a less expensive charger, we've taken our TwoLane ProCharger, removed the power supply, the fan, the cool custom paint, the temperature sensors, and the space saving top mounting battery position.

We kept the 1-6 amp charge rates, "no-button" charging, adjustable modes and delta settings, and backlit screen.

The Sportsman DC will still charge two batteries, and is even smaller than competing chargers that will charge only 1 battery!

And now at only $89!!
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Old 03-06-2005, 04:46 PM   #34
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Default 2.4Ghz Transmitter Prototype

I thought I would share the first prototype of the microwave transmitter made about a year ago. From the access logs on our website, it seems many of you are trying to find it!

It's here.
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Old 03-09-2005, 12:41 AM   #35
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Default ABS

I've heard about an "Antilock Brake System" aka ABS feature of some new transmitters, it pulses the brakes when you apply the brake.

Does this work, is it a real feature that will improve laptimes, or just another gimmick bell and whistle ?
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Old 03-22-2005, 03:41 PM   #36
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Default Re: Top Speeds

Quote:
Originally posted by nimble

Some simple math shows that each MPH in speed translates into a distance of .0176 inches each millisecond.
So at 30MPH, a 20ms period allows the car to travel 10.56 inches. If a servo update was missed during this period,
the car could travel over 21-inches before the next steering update.
Your system waits until you receive a ACK packet from your receiver before sending another update? I am worried.

If a packet is lost, say containing a steering update it should be a fraction of a second before it gets another one. Latency will not effect when the next packet is tramsmitted, it does effect how "old" the packet is when received.

Even the 62.5k you seem to bag out equals to the ability to send 62.5 bit's of data (7.8 bytes) every millisecond! If you can't squash 3 channels in to that there is something wrong :P
I see the Spectrum has 4096 resolution, that's 12bits so say 3 channels that's using 36 bits of a possible 62.5 if you where to transmit every millisecond.

*no protocol overhead was calculated so that may eat into the above 62.5k, I didnt bother to look it up ...
Also typed this after night shift so mistakes prolly made.. lol


Quote:
Originally posted by nimble

It also operates at 4 times the speed of Spektrum
How is the latency then? I assume by speed you mean the bandwith (250k?) or are you talking about the response time?

Last edited by au_Nightmare; 03-22-2005 at 03:46 PM.
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Old 03-22-2005, 04:45 PM   #37
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Hello, nice of you to take notice of our 2.4Ghz system. Some very exciting news will be forthcoming soon!

Our system transmits at 4 times the speed of the Spektrum, this means 4 times more information can be transmitted in the same time period,
or the transmission time is 4 times shorter. Shorter transmission time reduces the chances for interference and data loss.

It is not clear to me what others are claiming as "response time", but if this is how long it takes after you move a control for the information to be received by the car, our response time is less than 3ms.

We transmit a 10bit or 1024 positional value. This is in fact already more resolution than the controller pots or your fingers can discriminate.
More than just these 30bits must be transmitted.

We do not wait for ACK packets, the transmissions from the car are in fact not needed for control of the car.

Cheers,
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Old 03-22-2005, 04:51 PM   #38
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OK, does anyone else understand this?
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Old 03-22-2005, 06:00 PM   #39
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Quote:
Originally posted by Nrctc3
OK, does anyone else understand this?
Yep,

Translation:

Based on his understanding of the Spektrum being 56K bits per second, he's 4 times faster (meaning 200K)

the Ack packet is an Acknowledge Data Received, essentially, and he's saying that he doesn't do that, meaning he's RDP or Best Effort.
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Old 03-22-2005, 08:12 PM   #40
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Quote:
Originally posted by nimble

We do not wait for ACK packets, the transmissions from the car are in fact not needed for control of the car.
Cheers,
Oh ok, I am a little confused about this comment then-
"So at 30MPH, a 20ms period allows the car to travel 10.56 inches. If a servo update was missed during this period,
the car could travel over 21-inches before the next steering update.."

That would only be the case if you where sending 5 packets a second (every 20ms).
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Old 03-22-2005, 10:07 PM   #41
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Hey Boomer, you gonna be a SoCal this weekend? I will be there with 2.4ghz DART system in hand, thought you might like to see how the little transmitter feels in those big mitts.

Au,
My comment was simply pointing out how much distance a car will travel in the short time frame between updates to a servo or esc.

A ms is 1/1000 of a second, so there are 50 20ms periods in a second.
The Nomadio system had previously specified their radio had a "frame rate"
of 50 frames/sec, which is every 20ms.
I notice that now they have a 70 frames/sec rate reported, which is about every 16ms.
Spektrum only reports a "latency" of 5.6ms, it is not clear at all what that really means, or how the system transmits, other than it didn't work right in many cases until they changed it.

I will say that a radio module that
was designed to take an analog signal and transmit it directly at 75Mhz,
has been replaced by a unit that converts this analog signal into a digital form before being transmitted at 2.4ghz. This conversion by itself necessarily has latency
over the 75Mhz. It takes about 5.6ms
just to do this part itself, which is what I suspect is where their 5.6ms figure comes from.

We will be blowing them away shortly in any case!
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Old 03-23-2005, 10:10 AM   #42
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Nope - will be watching MarkA race rallycross in Corona - taking a week off.

Make a module and you could blow them away. Make an entire controller and I don't think you'll do it.

If for no other reason than feel - I know people who won't buy the M8 just because it feels wrong to them. . .same with the KO. . .etc.
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Old 03-23-2005, 03:17 PM   #43
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ok I understand about the framerate now and why you talk about missing a frame, distance traveled etc - you did not post that in first message so I only had half info

Quote:
Originally posted by nimble

A ms is 1/1000 of a second, so there are 50 20ms periods in a second.
Lol, yes sorry missing a 0

Quote:
Originally posted by nimble

I will say that a radio module that
was designed to take an analog signal and transmit it directly at 75Mhz,
has been replaced by a unit that converts this analog signal into a digital form before being transmitted at 2.4ghz. This conversion by itself necessarily has latency
over the 75Mhz. It takes about 5.6ms
just to do this part itself, which is what I suspect is where their 5.6ms figure comes from.

We will be blowing them away shortly in any case!
They where not designed to just transmit at 75Mhz, as you can get 27Mhz, 29Mhz, 40Mhz, 75Mhz etc modules. what type of data/info is available at the module pins?
Now , this analog to digital step - you say takes about 5.6ms. You are not converting analog to digital? how does your steering/trigger work? optical?

and I am with Boomer - you need to make modules not a new radio. (well make the new radio but also make modules) I plan to keep my R1 in my hands..

2.4G could become quite a mess if a heap of different 2.4G radio systems come online. Be nice if there was a agreed standard to "select a channel" etc..
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Old 03-23-2005, 03:56 PM   #44
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Quote:
They where not designed to just transmit at 75Mhz, as you can get 27Mhz, 29Mhz, 40Mhz, 75Mhz etc modules. what type of data/info is available at the module pins?
The analog data coming into the plugin frequency module is using the input to be transmitted directly at whatever frequency the module is built for. The data is the exactly the same data which is output to the servos/esc,
a 2ms period for each channel, where a ON signal for 1.5ms is "middle position", 1ms is "full left", and 2ms is "full right".
The reciever just redirects its input as output per channel as it gets it. This is a dirt-simple system designed to be cheap as possible. A true 2.4ghz replacement would do the same, but modulate the RF at 2.4ghz. A digital system must first decode the analog input before it can transmit it. That means waiting a full 6ms to get all three channels of data before it can even begin to transmit them.

A controller system such as our DART or Nomdio's SENSOR reads the user input from the controls and converts it into digital for processing just like an M8, etc does, but then it transmits it directly as digital data at 2.4ghz. There is no 6ms analog encoding.

Quote:
and I am with Boomer - you need to make modules not a new radio. (well make the new radio but also make modules) I plan to keep my R1 in my hands..
I'm with Boomer too..


Quote:
2.4G could become quite a mess if a heap of different 2.4G radio systems come online. Be nice if there was a agreed standard to "select a channel" etc..
It is already a heap of a mess in an unlicensed 2.4Ghz band that has a wide variety of devices sharing the band. Any radio system that is not designed to deal with that mess is going to have trouble sooner or later, and I believe that Spektrum has a lot of trouble ahead. Particularly in that they seem to deny any problem does or will exist. I'd plan to be returning their units again for more "fixes".
The FHSS vs DSSS debate has been raging for many years already in the wireless networking area, and as a veteran of that market, I already know who wins when it comes to interference.

Cheers,
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Old 03-23-2005, 07:56 PM   #45
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Quote:
Originally posted by nimble
The analog data coming into the plugin frequency module is using the input to be transmitted directly at whatever frequency the module is built for. The data is the exactly the same data which is output to the servos/esc,
a 2ms period for each channel, where a ON signal for 1.5ms is "middle position", 1ms is "full left", and 2ms is "full right".
Understood RE: the delay in obtaining latest position at module - I was hoping the 5 pins my JR module has was going to be something like:
1. +volts
2. -volts
3. ch1 position
4. ch2 position
5. ch3 position

Do you know what each pin does? You have me curious now...
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