This is normal for a brushed motor set up. Personally i would recommend using the latest technology and get a brushless ESC and motor. A brushed motor setup creates a TON of noise on the power rails.
Are you observing this with a scope or digital meter ?
if digital meter, then my bet is the supply is crashing.
The problem as far as using a regulator is that you need to insure that your vin (I.E. your battery) voltage will not go below the Vout voltage. If it does, which it seems like it is, you need to correct that first. If you dont then even having a regulator to power the cobra will do the same thing.
Take Bretts advise, and get a more capacity battery. I would get at the very least a 15C battery.
Yeah i use a digital meter ( only got it so probably the voltage goes really low …)
Larger capacity pack ? OK but the thing is that there is a caution sticker that the ESC is meant for use with 1100 -1500 mAH packs and Ni-MH only . I’d like to use 1800 mAH at least (there is a pack from a company in that capacity). Can i use it because i use the FEZ Cobra or will it damage the ESC as told on the sticker ?
OK, so your not using Li-Po packs, then forget what i said about the 15C thing i mentioned. That only applies to Li-Po packs
I am surprised to even see that warning, I have literally had over 50 different ESC’s that i have owned over the years and never saw that kind of warning. Is this a very old ESC ?
I can see no good reason for that kind of warning. mAH is the size of the gas tank. So having a larger battery capacity will only increase your run time. Although the only other issue is that when you go up in mAH capacity it will give you more surge capability that maybe that ESC cant handle or would get to hot. If ya got the coin, i would head up to your local hobby store and get one of the modern brushless ESC/motor setups. I think all of your problems you are encountering is because of your particular ESC.
They gave me an 9V 250mA 2,25VA Charger - do i need to change the charger ? is the anwser in the link above applicable to my problem ? Hopefully it will be ok i would try with around 2000-3000 mAH pack
charger for battery pack is all about how long it takes to produce the “fuel” to put it back into the battery. So your current charger should be fine; if you have a “fuel tank” twice as large then it will take twice as long to fill it. You could get a new one, but it’s somewhat unnecessary.
That guy is just plain full of crap. I dont know what your wall wart charger is rated as far as ma goes. but just because you slap a larger battery on it does not mean it will have to supply more chrage current. The only thing that will happen is that it will take longer to charge it.
I thought so too but had thought it may be a different thing with RC… but its elecricity same for all - anyways im not a great electric guy. This is why i wanted to know will a 3000mAH harm the ESP i think not, the only thing is that the ESC does not have a shutdown in case of a shortage.
But ensure me once more - a 3000 mAH bat pack will be ok as long as i stick to 7,2 V ?
Yup, you can even put a 10AH battery there as long as you stick to the 7.2v,
Personally, i would start looking into opto protection and some fuses so you dont do any harm to the cobra. If and when you start looking into a new ESC get one with opto input protection built in. This way if the ESC smokes it wont send any lethal voltage back up to the corbra and take that out.
Hmmmm… i dont know what your capable of because you mentioned this.
Probably the easiest would be to put a zener diode off the PWM and then a series resistor to the ESC control wire. But i will try to talk you into a new ESC first. You have a cobra board which is not cheap, and you also have a PC connected to it via USB which again is not cheap. So it would be in your best interest to pick up a $20-30 protected ESC.
This is a manual for my RC - my ESC is 003058 model … please at least take a glympse.
Is it called PCO ?
And i assume that the threat is through the PWM wire only ? ( Using the Power supply from the RC is ok ?)
I see your concern but i dont want to buy a new DC engine or ESC. Maybe there is an electric circuit for isolation of the PWM signal ? Plz Advise… this is supose to be a project for my thesis.
@ Update
Won’t a TRANSOPTOR do in this case ? But would i have to supply the voltage not from the +5Vin/Vout from The fez on the side of PWM input of ESC ?
yes, but if your powering the Cobra through the BEC circuit you could get hit there to, but unlikely.
There are a few things you can use, it all depends on the level you want to go at it with. Zener and resistor low level. fet to drive PWM wire, a but higher, opto obviously the highest.
this kind of Transoptor (is i good for the job ?) for optic isolation of the PWM signals.
What do you think (The BEC of the ESC looks like damaged - it gives low voltage and i have to use THE LM - i think that the VCC and GND of the BEC on the ESC touched and its dammeged ever since)
ALso i bought a 3000 mAH 7,2 Ni-MH battery and we will see what is going to happen, i plan on using the 1100 mAH for the FEZ Cobra (+ additional stuff attached to it) for power supply. Hopefully this will do :D. Any suggestions ?
Cobra has 2 vregs. First one takes input from board power jack and outputs 5v to corresponding rail (5v in/out). This 5v is used to power lcd back light circuit. The second vreg inputs this 5v and outputs 3.3v to power the processor and lcd display. I use the 7805 regulator which can input up to 30v and outputs 5v and up to 1A. The output of 7805 I connect to Cobra’s 5v in/out rail.
i would try with around 2000-3000 mAH pack
and i have to use THE LM - i think that the VCC and GND of the BEC on the ESC touched and its dammeged ever since)