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Topic: Servo Motor doesn't move although 5V (Read 5713 times) previous topic - next topic

OldSteve

#15
Nov 21, 2015, 10:46 am Last Edit: Nov 21, 2015, 10:48 am by OldSteve
Thank you OldSteve, the first precise answer :)

LiPo sounds nice, also a 7.4 Voltage is fine.
Well, i send sensorvalues via 433 MHz on this arduino, who shall controll 2 Servo-Motors. So with 4800mAh, it could be 4-5 hours? Sounds nice.
So i had a look on this battery:

http://www.kotte-zeller.de/LRP-LiPo-Akku-7-4V-3800mAh-30C-Hyper-Pack-Multi-Plug-Hardcase-430215.htm?websale8=kotte-zeller-shop&pi=902017


Well, it has a nice capacity but its way too large and weights to much i think... :( Never thought, that battery-management is so hard.

My 5V regulator is a linear one. "LM1084" (http://docs-europe.electrocomponents.com/webdocs/0780/0900766b807800b5.pdf)

EDIT:
I found this one:

http://www.kotte-zeller.de/Dynamite-Reaction-LiPo-Akku-7-4V-4000mAh-50C-Sub-Hardcase-EC3-DYNB3800EC.htm?websale8=kotte-zeller-shop&pi=901974

its smaller than the other one, has more capacity
Li-Po is as good as it gets in terms of energy density, (energy for weight/size). Both of those batteries sound fairly good.

With a linear regulator, you'll probably need a heatsink, especially when the battery is fully charged and the load is high. On my little robot, I currently use two LM2940CT-5 LDO linear regulators with small heatsinks, but have a 5V switching regulator on order, to reduce heat dissiaption and power wastage. That's for 3 servos, though - a higher load than your 2-servo project.
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

Rachmaninow

#16
Nov 21, 2015, 11:19 am Last Edit: Nov 21, 2015, 11:32 am by Rachmaninow
Nice okay.

So i will connect the Li-Po to the servos via LDO. Parallel to that, i connect it to the arduino (Vin). Also parallel to that, i want to power my 433 MHz module (Voltage increases range, 5V isn't very good). Maybe I can increase the voltage with this LDO:

http://www.exp-tech.de/pololu-12v-step-up-spannungsregler-u3v12f12?gclid=Cj0KEQiAycCyBRDss-D2yIWd_tgBEiQAL-9RkiuCb2OUDoP0vOXj4krR8xHNrMQWXvKkk9hAbmFbRksaAhMl8P8HAQ

to 12 V? So i get more range?

Paul__B

you could use that LDO to get the 5v, and put the 5v output of that into the 5v pin - but if you do that, you must not connect it to USB while it's powered that way, lest you risk damage to the board
This is curious.  How could applying 5V to the VCC pin (whilst connected to USB) damage the board?

OldSteve

Nice okay.

So i will connect the Li-Po to the servos via LDO. Parallel to that, i connect it to the arduino (Vin). Also parallel to that, i want to power my 433 MHz module (Voltage increases range, 5V isn't very good). Maybe I can increase the voltage with this LDO:

http://www.exp-tech.de/pololu-12v-step-up-spannungsregler-u3v12f12?gclid=Cj0KEQiAycCyBRDss-D2yIWd_tgBEiQAL-9RkiuCb2OUDoP0vOXj4krR8xHNrMQWXvKkk9hAbmFbRksaAhMl8P8HAQ

to 12 V? So i get more range?
That should give good range. Make sure you use good power supply filtering/decoupling though, to ensure there are no remnants of the switching on the output.
Are you sure you can't get enough range just with the 7.4V battery? You might not need to step up to 12V at all.
Having said that, though, I've had my best results by powering those cheap 433MHz RF transmitters from 12V. I use little A23 12V batteries in my alarm system remote controls - they don't get used very often so the battery lasts for months.
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

Rachmaninow

Mhm, yea i power the transmitter with 9V but its still not enough range. Maybe 20 Meters, without any walls - thats really poor. Also I use 17,3 cm long spiral-antennas (wire) at transmitter and receiver. Is it necessary to power the receiver with more than 5V to get a better range?

I also use this "cheap" 433MHz RF transmitters; i think the same like you. What did you do to extend the range?

OldSteve

Mhm, yea i power the transmitter with 9V but its still not enough range. Maybe 20 Meters, without any walls - thats really poor.
That is poor. I get 20+ metres, through a brick wall and a steel garage door.

Quote
Also I use 17,3 cm long spiral-antennas (wire) at transmitter and receiver.
I use exactly the same. Just make sure they're exactly 173mm for maximum effectiveness.

Quote
Is it necessary to power the receiver with more than 5V to get a better range?
I also use this "cheap" 433MHz RF transmitters; i think the same like you. What did you do to extend the range?
As I mentioned, I power the transmitter with 12V to get maximum range. I still power the receiver with 5V, though. That's the maximum allowed with the receivers that I use.

Perhaps there's more RF noise where you are, reducing the effective range. There isn't a whole lot you can do about that, unfortunately. Perhaps a better antenna, a dipole, or a 1/2 wave instead of 1/4 wave.
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

Rachmaninow

#21
Nov 21, 2015, 12:55 pm Last Edit: Nov 21, 2015, 01:00 pm by Rachmaninow
Okay, i tried now a spiral antenna and a normal one. the spiral one had a range of ~10 metres. The normal one had ~20 metres (eye contact). So i will use the straight version

mhmm... thats shit :( So i need the 12 V in every case. Does 12V on RX-side increase the range? Does a second 17,3cm long antenna increase the range? (V-form)

Can i use another more powerful 433 MHz transmitter without changing my code? I use VirtualWire to send data.

jremington

Quote
Does 12V on RX-side increase the range?
That will destroy the receiver.

For best range, use a dipole antenna for both receiver and transmitter as shown below. Connect "GND" to one end of the dipole and "ANT" to the other, as in the picture. I get 500 meters, open, line of sight.

For 434 MHz, the optimum distance between the dipole ends is 32.8 cm for #14 AWG wire.


Paul__B

Okay, i tried now a spiral antenna and a normal one. the spiral one had a range of ~10 metres. The normal one had ~20 metres (eye contact). So i will use the straight version
The length of the wire used for a "helical" (what you call "spiral") antenna is not the same (not even close) as a quarter wave "whip".  To use helical antennae you need either to have some (very) sophisticated mathematical modelling, or the equipment to test and tune it.

The performance of a helical antenna will always be greatly inferior to a quarter wave "whip".  As a first understanding of antenna behaviour, two things are critical, the length - literally you need to catch as big a piece of the signal as possible and similar for transmission - and resonance; being properly tuned.

The simplest way to implement these requirements is as jremington illustrates, to attach a dipole of the correct calculated length directly to the two antenna connections of the module.  Note that if you attach only one antenna wire, then you are expecting the random arrangement of your other wiring to act as the other, the "ground plane", and it is quite unlikely to do this effectively, so even though your "whip" is the correct length, it will be out of tune.

This entirely accounts for the wild variation in performance of these modules as people perceive them.

OldSteve

#24
Nov 21, 2015, 11:00 pm Last Edit: Nov 21, 2015, 11:03 pm by OldSteve
The length of the wire used for a "helical" (what you call "spiral") antenna is not the same (not even close) as a quarter wave "whip".
I wasn't aware of this. An article in "Silicon Chip" magazine recommended using the same length. ie 173mm for a 1/4 wave @ 433MHz.
Armed with your info, I just did a search and found a calculator:-
http://www.daycounter.com/Calculators/Helical-Antenna-Design-Calculator.phtml

For longer range and/or more reliability, rather than mess around with larger, more complex antennas etc, I just use APC220 serial RF transceivers. Line-of-sight range up to 1000m. They just use a short SMA connector "rubber ducky" antenna.
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

Rachmaninow

#25
Nov 22, 2015, 12:23 am Last Edit: Nov 22, 2015, 12:32 am by Rachmaninow
Wow, Thank you all for your answers and your time.

So, The correct way to implement this dipole antenna is, that i connect a 17,3 cm wire to ANT, and a 17,3 cm wire to GND? Or do i have to use other lengths or materials? I use silver-wire.

500 meters would be soooo nice to have! I would be happy at atleast 100 meters :lol: :)

@OldSteve:
according to you suggestion to use another transceiver, i googled it:

https://allodox.wordpress.com/2013/05/01/configuring-an-apc220-rf-transceiver-with-arduino/

Looks like I need to implement another library, and that is the point. I have a intensive time-probleme, so I think i will try the Dipol-antenna! But thank you anyway!



Also i will try to reduce the Baud-speed. Actual i us "vw_send(5500)", maybe its too fast. I`ve readt that reducing this rate will also increase the range.

OldSteve

#26
Nov 22, 2015, 12:38 am Last Edit: Nov 22, 2015, 12:41 am by OldSteve
@OldSteve:
according to you suggestion to use another transceiver, i googled it:

https://allodox.wordpress.com/2013/05/01/configuring-an-apc220-rf-transceiver-with-arduino/

Looks like I need to implement another library, and that is the point. I have a intensive time-probleme, so I think i will try the Dipol-antenna! But thank you anyway!
Just normal serial, at up to 115200 baud if you're sending less than 256 bytes at a time. (19200 baud for continuous transmission). This is much faster than the maximum data rate of most of those cheap transceivers. For the ones that I buy, the TX is max 8kbps, RX is 4.8kbps. Not even in the same ballpark as the APC220.
And you wouldn't need to add any library at all if you use hardware serial. If "SoftwareSerial", just that library. No others are needed.
The only downside with these modules vs the el-cheapo type is cost.
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

Rachmaninow

Sounds easy.

I try a dipol antenna and reduce the transmission speed. Then i Will see if I need the suggested antennas.
But normally i dont have the time to order those and creat a new hardware design... costs are not a problem..

OldSteve

#28
Nov 22, 2015, 01:50 am Last Edit: Nov 22, 2015, 01:51 am by OldSteve
Sounds easy.

I try a dipol antenna and reduce the transmission speed. Then i Will see if I need the suggested antennas.
But normally i dont have the time to order those and creat a new hardware design... costs are not a problem..
If cost isn't a problem, but speed is an issue as you mentioned earlier, perhaps you should buy a decent transmitter/receiver or transceiver pair. That also allows a small, compact setup rather than bulky dipole antennas.
Unless you're already committed to a PCB design, it's only the work of an hour or two to make the changes required. (You've already spent longer than that just discussing the issue.)
Please do not PM me for help. I am not a personal consultant.
And others will benefit as well if you post your question publicly on the forums.

Paul__B

#29
Nov 22, 2015, 10:53 am Last Edit: Nov 22, 2015, 10:54 am by Paul__B
The "take-home message" here is that a proper antenna - the dipole - is substantially cheaper and probably more effective than a massive increase in power.

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