Author Topic: Fans and RC (Read 13761 times)

gamefreak · « **Reply #30 on:** October 19, 2007, 03:35:45 PM »

it needs to be cheap

this out runner: http://cgi.ebay.com/2408-21-Outrunner-Brushless-Motor-20-Amp-ESC_W0QQitemZ220142280770QQihZ012QQcategoryZ34056QQtcZphotoQQcmdZViewItem

seems like it would work, but the current draw is horrible, also what is ESC?

ed1380 · « **Reply #31 on:** October 19, 2007, 04:16:10 PM »

3.6 mins is @ full power. if you run it at full power, it's gonna go into orbit

something like this. http://cgi.ebay.com/3500kv-Brushless-Motor-30A-ESC-for-RC-Helicopter-BKU_W0QQitemZ160169223698QQihZ006QQcategoryZ34056QQssPageNameZWDVWQQrdZ1QQcmdZViewItem#ebayphotohosting
airman also said to get something like it

and it comes with a ESC(electronic speed controller) so just plug it into a servo type receiver and you're good to go.

that way a 2 channel receiver will power thrust and steering (servo and the motor) with no additional modifications

and the idea with the styrafoam is very good. I would have used some paperboard tube, but this way you can stick the motor mounts in to the foam

gamefreak · « **Reply #32 on:** October 19, 2007, 05:51:58 PM »

yea, i originally planned tobuild the base out of balsa, but styrofoam is lighter and i can make it into any shape.

so with one of those and an ESC then all i have to do is NOT push all the way forward on the remote(I can imagine my hovercraft skirt exploding on start up), i could also wire a resistor in to limit more current couldn't i?

Admin · « **Reply #33 on:** October 19, 2007, 06:17:12 PM »

just a thought . . . have you considered just buying a RC hovercraft and then hacking into the wiring?

ed1380 · « **Reply #34 on:** October 19, 2007, 06:23:43 PM »

Quote from: gamefreak on October 19, 2007, 05:51:58 PM

yea, i originally planned tobuild the base out of balsa, but styrofoam is lighter and i can make it into any shape.

so with one of those and an ESC then all i have to do is NOT push all the way forward on the remote(I can imagine my hovercraft skirt exploding on start up), i could also wire a resistor in to limit more current couldn't i?

the more you you press teh joystick the more power is sent to teh motor.

you can use a pot on the lift motor and set it to whatever's best

dang all of this is making me want to build something too.

gamefreak · « **Reply #35 on:** October 19, 2007, 06:45:23 PM »

Quote from: Admin on October 19, 2007, 06:17:12 PM

just a thought . . . have you considered just buying a RC hovercraft and then hacking into the wiring?

but where is the fun and headaches in that?

Also, since this is for a school robotics club i need an excuse for racing toys down the hall, and since building from scratch gives good building experience and can help the kids that are newer to building learn how to optimize their designs.

so i found a farily cheap motor: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220151725619&ssPageName=MERC_VI_RSCC_Pr4_PcY_BIN_Stores_IT&refitem=220151725522&itemcount=4&refwidgetloc=active_view_item&usedrule1=StoreCatToStoreCat&usedrule2=CrossSell_LogicX&refwidgettype=cross_promot_widget

that gives me 1750 rpm per volt, so with 7.2 volts i get 12600 RPM, which should be more then enough.

ed1380 · « **Reply #36 on:** October 19, 2007, 10:14:43 PM »

that motor looks like it needs lipo battteries. or at least that's what teh ESC is configured for

gamefreak · « **Reply #37 on:** October 20, 2007, 02:53:59 AM »

it says NiMH and NiCD also work

but can i just hook up one of those motors without an ESC and give it some resistors? I don think that the motor used for lift really needs to be speed controlled, just sit at a set speed the whole time.

bulkhead · « **Reply #38 on:** October 20, 2007, 04:27:36 AM »

Get a transmitter/receiver/servo combo at any hobby shop ($40-$60). Get an ESC (electronic speed control) also from a hobby shop, they start at $40-$50.

Get 2 cheap DC motors like this one here: $3 each http://www.radioshack.com/product/index.jsp?productId=2102822&cp=&parentPage=search

Buy two CPU fans or find two old ones, remove the blade and mount on the 2 DC motors. CPU fans/airplane props/custom propellers should work. One motor is for lift, the other for thrust. Put a tight fitting duct around the lift fan to increase efficiency.

Wire the 2 DC motors in parallel to the ESC. Thus when no throttle is applied, the hovercraft will come to rest. This will make it easier to control since it is not drifting everywhere (there's essentially an auto-brake, friction). As the thrust fan turns on, the lift fan does too and it begins to move. Use the steering servo to create a rudder steering system.

Rechargeable (NiMH, NiCd) AA batteries should work for this size. Any smaller and the current output of the batteries may not be sufficient, any larger and they will be too heavy. Do not use alkaline batteries, which have high internal resistance. Just place the batteries so that the hovercraft is balanced.

airman00 · « **Reply #39 on:** October 20, 2007, 05:08:22 PM »

Those cheap hobby motors can be bought elsewhere for less that $1.

I'm also not sure if they are strong enough to provide lift.

gamefreak · « **Reply #40 on:** October 20, 2007, 07:54:59 PM »

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220151725619&ssPageName=MERC_VI_RSCC_Pr4_PcY_BIN_Stores_IT&refitem=220151725522&itemcount=4&refwidgetloc=active_view_item&usedrule1=StoreCatToStoreCat&usedrule2=CrossSell_LogicX&refwidgettype=cross_promot_widget

How about if i take one of these(comes with an ESC) and then use one of the ducted styles where i only have the one fan and then put a duct in the back right behind its exhaust and make it about as large as 15% of the fan, then 25% of the thrust is being used for lift and i only need one motor, then just build a rudder out of balsa and as servo?

say using this prop: http://stevensaero.com/shop/product.php?productid=16250

which according to the ebay page gives me 16 ounces of thrust, which with the motor, battery and receiver added together i get 14.1 Oz of weight.

airman00 · « **Reply #41 on:** October 20, 2007, 08:16:52 PM »

Sounds good. That motor should provide all the thrust you need (22 ounces of thrust)

Your rudder idea is good but keep in mind that the steering won't be as good as the differential fan. Sounds good in concept but you'll run into problems with the ducts.

( you don't really need ducts , but using ducts will maximize thrust and lift)

Keep us posted with your project!

,Eric

ed1380 · « **Reply #42 on:** October 21, 2007, 07:54:55 AM »

you mean something like this

i think it'l work, but you'll need to adjust the duct size until you get it right

gamefreak · « **Reply #43 on:** October 27, 2007, 08:42:35 PM »

I just discovered a potential problem, the receiver needs 4.8-6 volts, the ESC requires 7.2-12.6 volts, so i need to solder in a resistor between the ES and receiver, correct?

Admin · « **Reply #44 on:** October 27, 2007, 08:54:23 PM »

Im assuming you are trying to power the ESC and the reciever with the same battery right?

Hmmm see if the ESC works on just 6V anyway . . .

Otherwise, a resistor won't work. You'd need a voltage regulator.

Or you can use two seperate batteries if you have a 6V or 4.8V around.

airman00 · « **Reply #45 on:** October 27, 2007, 09:04:06 PM »

get a voltage regulator from fairchild semiconductor- free samples

I always try to regulate my voltage so that my parts are getting what they need.
( remember to decouple the regulator)

gamefreak · « **Reply #46 on:** October 27, 2007, 09:43:52 PM »

yea.. umm... those 3 wire things are confusing, batteries only have 2.

Also, it keeps telling me to get a battery rated for amps of the ESC, which is 20 amps, no battery has that much current, i found a lithium battery that says it is rated for 30 AMPS but has 2500 mAh, so how is this comparable to a NiMh?

bulkhead · « **Reply #47 on:** October 27, 2007, 09:50:33 PM »

Most hobby ESC's should be able to provide power to the receiver (3 wires: gnd, power (regulated to +5v or something usable), and signal). You only need to connect the battery to the ESC. Batteries normally do not have 'amp' ratings (amp-hour or milliamp-hour refer to capacity), but you will probably want a NiMH battery unless you want to spend the extra $$ for lipo. '2/3 A' type cells are generally quite popular (and small) and can probably supply around 20 amps or so peak (depending on the brand/quality of cells you get). For comparison, 'sub-c' RC car battery packs can usually discharge at around 35 amps. If you go this route, you will need a good peak charger.

gamefreak · « **Reply #48 on:** October 28, 2007, 08:43:52 AM »

ok but the receiver requires 1.2 volts less then the ESC is getting, and even though it porbably wont do something, how do i hook up a voltage regulator to it? also, i thought voltage regulators didnt come in 6 volt, i thought they came in 5 and other random numbers that are commony used..

Admin · « **Reply #49 on:** October 28, 2007, 11:20:22 AM »

gamefreak, can you link us to a datasheet of your ESC?

what bulkhead is saying is that the ESC probably has a voltage reg built in to power the reciever for you . . . but im not sure so I wanna check the sheet first . . .

the ESC is rated up to those numbers, its not a requirement. if you give it more than those 20amps it will probably melt/explode/fry . . . if your battery is rated to 30A, don't worry about it - as long as your motors draw less than 20A then you are fine. but as a beginner I would recommend staying away from lithium batteries as they are dangerous if you don't use them properly.

and voltage regulators come in all types of voltages, including negative ones

there are three pins to them - ground, battery +, and regulated output

gamefreak · « **Reply #50 on:** October 28, 2007, 11:23:18 AM »

i dont exactly have a datasheet, but i have an ebay page: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220151725619&ssPageName=MERC_VI_RSCC_Pr4_PcY_BIN_Stores_IT&refitem=220151725522&itemcount=4&refwidgetloc=active_view_item&usedrule1=StoreCatToStoreCat&usedrule2=CrossSell_LogicX&refwidgettype=cross_promot_widget

which says:POWER UP 20 amp ESC Specifications:

Weight = 0.6 ounce

Dimensions = 1.75 x 1.0 x .3 inches

Current = 20 amp continuous (25 amp burst)

Input = 6 to 13 volts

Battery: 2 & 3 cell Lipo or 6 - 10 NiMh/NiCD

BEC: 2 amp 2 cell Lipo = 4 to 5 servos 3 cell Lipo = 3 to 4 servos

PWM: 8 KHz

FET: 12

if a regulator was needed,is this how i wire it?

Im also a little confused on how the ESC powers the receiver and gets signals from it from only one wire, it says to plug it into channel 3 of the receiver, but mine only has 2 and a battery plugin, if i pkug it into the receivers battery plguin i dont see how it gets a signal, if i put it into another channels spot i dont see how it gets power...

bulkhead · « **Reply #51 on:** October 28, 2007, 12:59:33 PM »

The receiver sends signals to the servo and ESC through PWM, Pulse Width Modulation. Essentially, the length of time the pulse is high (or low, it's one of the two) indicates the position/speed the servo/ESC should go to. Thus, the signal can be sent on 1 wire (the white one), only requiring that both the receiver and servo/ESC share a common ground (black wire).

The red wire is power. It is usually between 4.8V and 6V. Power only needs to come from one source, and in most RC cases, it is the ESC that provides it (regulated to 4.8-6V) through it's 3rd red wire going to the receiver (remember only signal and ground are required for communication). The receiver and servo(s) use the power from the ESC. If you choose to use a separate battery to power the receiver and servos, you will need to disconnect the red wire from the ESC going to the receiver so you dont have two conflicting power sources.

I would assume that that ESC in the auction provides regulated power (since it has the 3rd red wire), but you may want to double check.

gamefreak · « **Reply #52 on:** October 28, 2007, 01:17:42 PM »

but where would i plug the ESC into the receiver?

the ESC has the 3 wire servo plug, but the receiver only has 2 pins for power, and i dont think plugging power into an output on a receiver will work, if anything i think i would fry it.

The red and black wires on the left connect to battery, the 3 wire plug goes to receiver, so im confused on how the receiver receives power and sends the signal when no wire goes to the receivers power pins.

my receiver: http://www.servocity.com/~servo/html/hp-2rnb_am_rx.html

Admin · « **Reply #53 on:** October 28, 2007, 04:33:14 PM »

Im fairly sure you won't need a voltage regulator. Just plug the ESC into the reciever (using that servo 3 wire connector), and plug the battery into the ESC and you are done.

But just to make sure, before plugging it into the reciever, use a multimeter to measure the output in that servo connector first. As long as its under 6V you are fine.

gamefreak · « **Reply #54 on:** October 28, 2007, 05:03:47 PM »

i dont get it still, the receiver cant receive or send a signal without any power, and the ESC cant receive a signal unless plugged into one of the channels on the receiver.

So which pins on the receiver do i plug this into? or do i have to split it and have two go to battery and one go to the correct pin of the receivers channel one?

Can the ESC just plug directly into a receivers channel and power the receiver? ie. plug the connector into channel two and then it will work?

Admin · « **Reply #55 on:** October 28, 2007, 05:08:30 PM »

Quote

Can the ESC just plug directly into a receivers channel and power the receiver? ie. plug the connector into channel two and then it will work?

yes!

the ground/power pins in your reciever are all connected together - the battery can be connected in any one of them.

gamefreak · « **Reply #56 on:** October 28, 2007, 06:03:20 PM »

Ahh, see thats what i didnt get, i figured that applying the voltage into the output would create pretty sparks, so if i wanted channel one to control the thrust i would just plug it into their and everything would work, so then if i plugged something into the battery input on the receiver it would act as if it had continuos voltage.

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Author Topic: Fans and RC (Read 13761 times)