jdwiflyrc

My Feedback: (31)

Has anyone used a powersupply in place of the batterys in a tx and rx, If so did you have any interference with the operation of the unit.

I would like to know of your experiences, problems, etc, and if the cheep wall plug type would work ok.

pettit

My Feedback: (23)

I've never tried that one, but if you want to give it a try, make sure your extension cord is very long, and lightweight!

modeltronics

My Feedback: (27)

I use a lab type power supply all the time on the bench. It works great.

Pete

wildblueyawner

Yes, I use a cheapo wall power supply (AC adapter) when doing radio installations and servo / linkage adjustments on the bench. Very handy. Considerations:
1) don't exceed pack voltage
2) adapter must have enough current output (normally not an issue unless running several servos or at high torque)
3) ensure proper plug polarity

jdwiflyrc

My Feedback: (31)

Hi Dick,

I figured someone would bite, I just didn't figure on it being you.HA!!! HA!!! HA!!!

It's good to hear from you, keep in touch.

I have a 4 ch ground unit that I plan to play around with and did not want to keep checking the battery charge.

Modeltronics and Wildblueyawner,

what milliamp should I use for the 9.6 tx and for the 4.8 RX as I don't think that I will be overloading with too many servos or high torque servos.

Thanks for the replies and keep em fly'in, John

Lynx

I've had problems with this before. It's easy enough to fix, the biggest problem with wallwarts is the ripple because ripple doesn't exist on a battery packs. Putting a bunch of large value capacitors (Radio Shack grab bag parts work well) will smooth it out enough. Just make sure you do any final tests on a battery.

wildblueyawner

The supply must be able to provide current at least equal to the drain of whatever its powering.

Tx drain can be determined from battery capacity divided by operating time, e.g. if your pack is 1500 mAh and lasts 3 hours off a full charge, then the Tx's drain is 1500 mAh / 3 hrs = 500 mA.

For Rx power (assuming this is for radio setup/adjustment purposes), I'd assume one stalled servo which, I think, amounts to about 250 mA for a standard servo. Heavy duty or digital servos are maybe twice? that.

Lynx makes a good point about another issue - Most wall AC adapters are not regulated. Voltage ripple might not cause a problem, but I'd be concerned about voltage possibly going too high at low currents. To be safe with an unregulated supply, use one rated at the low end of the voltage you need, e.g. I use a 4.5V unit for Rx supply.

The safe approach is to use a regulated unit which costs little more than unregulated (I'm going to go this route to end my paranoia of frying something). Here are some regulated units that should work well for 9.6V Tx and 4.8V Rx systems (hope these links work!):

5V, 500 mA:
http://www.jameco.com/cgi-bin/ncomme...&search=164101

5V, 2400 mA:
http://www.jameco.com/cgi-bin/ncomme...&search=196470

9V, 1670 mA:
http://www.jameco.com/cgi-bin/ncomme...&search=161550

I believe 9.6V systems will handle voltages somewhat over 12V (confirm this), in which case a 12V adapter might be better.

12V, 1000mA:
http://www.jameco.com/cgi-bin/ncomme...&search=170245

Lynx

Stalled servo current even on a simple servo is closer to 700ma's

wildblueyawner

Lynx - thanks for disputing my 250 mA figure. It got me to do a search leading to this data for servo current drain at various loads (go to bottom of page): http://www.fly-imaa.org/imaa/hfartic.../v11-4-44.html showing stalled-servo values way higher than what I anticipated. Since I'm working a giant-scale project, this "revelation" is valuable to me.

Lynx

Stall current on electric motors is always insanely high, this is of course relative on RC equipment => It's just the way inductive loads work. If you have a good multi meter you'll notice that the peek currents are even higher than that because of how inductive loads work, part of designing motors.

wildblueyawner

I bought a regulated 5V wall adapter rated to 1000 mA - Works great. Details in new thread here

jdwiflyrc

My Feedback: (31)

Hiya Wildblue,

Thanks for the input, I already have an adapter like that so I will get one of the A/C--D/C 5V power supply.

Thanks again and keep em fly'in.

Have a good EASTER, John