R/c switch from servo amp ?

[Terry Rigden]

I want to switch LED nav lights on and off in flight. The load is about 40mA at 5V
I've heard its possible to do this with a servo amplifier but how ?

Is there a better / lighter way of doing this

Thanks

Terry

[shanghai_fool]

Take an old used servo, any size will do for 40ma. Center it with a radio if possible. Open it up and remove the motor. Place LED with series with 150 ohm resistor between the 2 motor terminals on the servo amp. It should light when tx control is moved in 1 direction. It it is not the direction you need, then reverse the LED to the other motor terminal. .

[pmackenzie]

You could lose a bit more weight by replacing the pot with two resistors.
Just measure each side from the centre tap to get the values.

Pat MacKenzie

[Terry Rigden]

Thanks guys. I'll start butchering a servo

Terry

[shanghai_fool]

Feel free to get rid of the mechanics and case as well. If the pot cannot be removed from the mechanics, (it is usually pressed on the output gear on the smaller servos), replace with 2.4k or 2.7k resistors.

[heli_ebook]

Ha! Cool.... this is ALL the info I wanted when I came in here 2 mins. ago. Thank you!

[HoaRC]

WOW, I just made a couple of RC switches from servos! I can tell you how! Pm me.

It's easy.

You need

#1 any servo
#2 relay such as NAIS (Panasonic) 10A SPST RELAY, 5 volt coil http://doc.chipfind.ru/pdf/nais/dk1a5v.pdf

solder out the servo motor
connect one servo motor lead to relay coil prong #1
connect the black ground servo wire (there are three red,white, and black) to relay coil prong #2

Now you have a relay switch that can handle up to 10 Amps of current!

-Post up your rc setups at http://rcgearing.com

[HoaRC]

Anybody who wants to make a 10Amp rc switch I can send you a servo and a relay that will work. Pm me if you are interested.

[mrfliboy]

I just tried this and lo and behold it works. Now lets say you have only a 4 channel receiver, you are already using 3 channels. If I want to put this on the 4th channel and trigger it on by moving the stick one way and trigger it off the other way no go correct. Right now it'll only stay on with the stick held in on position.

Just curious if theres another way to do what i"d like. I am able to trigger it on and off by moving the trim switch which should be OK.

BTW Thanks Terry for giving me another project to attempt. LOL

[Ron W3FJW]

Edit: Deleted double post.

[Ron W3FJW]

If you have a retract channel and are not using it for retracts, might be able to use it for this application, or any channel that's controlled with a switch. A reed relay would work also if the contacts have enough current rating for your application. Could use two or three in parallel for increased currents.
Might have to program your end points.

[mrfliboy]

Thanks Ron, in this application a std 4 channel radio is also being used. Now mind you I have the radios with more channels. Its the challenge of the hunt to find out how to make it work cheaply. LOL

[vintage1]

For lights, use a cheap small brushed ESC.

You can even dim them!

At 40mA a servo will obviously work too.

Just put a diode /resistor in series with each LED and replace servo motor with the combo, and set output pot more or less central.

[mrfliboy]

For lights, use a cheap small brushed ESC.

You can even dim them!

At 40mA a servo will obviously work too.

Just put a diode /resistor in series with each LED and replace servo motor with the combo, and set output pot more or less central.


Not meaning to Hijack Terrys thread but my quest I believe is still being missed. I'm a tad slow sometimes LOL.

4 channel Radio. 3 channels are used already. 4th channel lets say rudder is wanting to be used as the on/off switch. Currently I have to hold the rudder over to the right to keep the lites lit. Releasing the rudder lights go off. Now mind you I am able to keep the lights on by moving the trim lever. Simple enough.

What I am wondering how would one go about using the rudder to flip the lights on, move tthe stick to the right, blip the stick to the left lights go off. Of course using just the existing servo parts as we are now.

[Dan Baldwin]

You might be able to add hysteresis by adding a resistor from one motor output lead to the center of the voltage divider, wether it be the original pot, or two fixed value resistors. If the resistors you are using are 2.2 K or so, you might want to use a 22K or greater hysteresis resistor. If you don't get the effect you are looking for, try hooking the resistor to the other motor output lead.

Dan

Not meaning to Hijack Terrys thread but my quest I believe is still being missed. I'm a tad slow sometimes LOL.

4 channel Radio. 3 channels are used already. 4th channel lets say rudder is wanting to be used as the on/off switch. Currently I have to hold the rudder over to the right to keep the lites lit. Releasing the rudder lights go off. Now mind you I am able to keep the lights on by moving the trim lever. Simple enough.

What I am wondering how would one go about using the rudder to flip the lights on, move tthe stick to the right, blip the stick to the left lights go off. Of course using just the existing servo parts as we are now.

[mrfliboy]

You might be able to add hysteresis by adding a resistor from one motor output lead to the center of the voltage divider, wether it be the original pot, or two fixed value resistors. If the resistors you are using are 2.2 K or so, you might want to use a 22K or greater hysteresis resistor. If you don't get the effect you are looking for, try hooking the resistor to the other motor output lead.

Dan


Howdy Dan, been awhile.

Now theres a new word Hysteresis. Right now all that I've done is put a 150ohm resistor in line off one of the motor leads to the led. The pot is still originally hooked up to the servo board. I believe the trim on/off is fine. I'm just curious to how the voltage could be triggered on/off by moving the tx stick and stay on or off.

[Dan Baldwin]

Try hooking the 22K or so resistor from the same place you have your 150 ohm resistor, to the center connection of the pot. If it doesn't work, or if you end up with a large linear region (LED dims instead of turning on/off cleanly), move the resistor to the other motor lead.

I haven't tried this, so I don't know if it will work.

Dan

Howdy Dan, been awhile.

Now theres a new word Hysteresis. Right now all that I've done is put a 150ohm resistor in line off one of the motor leads to the led. The pot is still originally hooked up to the servo board. I believe the trim on/off is fine. I'm just curious to how the voltage could be triggered on/off by moving the tx stick and stay on or off.

[mrfliboy]

Try hooking the 22K or so resistor from the same place you have your 150 ohm resistor, to the center connection of the pot. If it doesn't work, or if you end up with a large linear region (LED dims instead of turning on/off cleanly), move the resistor to the other motor lead.

I haven't tried this, so I don't know if it will work.

Dan


Thanks as usual Dan, I'll give it atry later today.

[HoaRC]

For lights, use a cheap small brushed ESC.

You can even dim them!

At 40mA a servo will obviously work too.

Just put a diode /resistor in series with each LED and replace servo motor with the combo, and set output pot more or less central.

I was waiting for Vintage to pitch in. A great answer as always from the MAN himself! :D

[Terry Rigden]

I just tested my lights set up and it works! Thanks guys

I'm a bit puzzled at how much current the servo amp is taking - about 50 mA lights n and 10mA lights off , that in addition to teh current drawn by the LEDs
I was expecting more like 10 -20. It's out of an old Hitec 16G servo

Not that its a problem switching on all the lights adds 100mA to the operating curent and out of 3.5A to fly the thing that's trivial.

I'm dead chuffed but the missus thinks it's a flying Christmas tree. Now there's and idea pass me the Depron please.

Regards

Terry

[mrfliboy]

Try hooking the 22K or so resistor from the same place you have your 150 ohm resistor, to the center connection of the pot. If it doesn't work, or if you end up with a large linear region (LED dims instead of turning on/off cleanly), move the resistor to the other motor lead.

I haven't tried this, so I don't know if it will work.

Dan


Congrats Terry

Dan, as usual I'm a bit confused. What I tried so far is I put the 22k resistor in line from one motor lead to the center of the pot and had the led hooked up to the other motor lead and the original pot wire. Nothing happened.

Than I tried swapping motor leads nothing.

Than for kicks and giggles I tried one motor lead to led and the led to the negative on the servo wire, and the 22k inline on the center of the pot. Nothing.

Hooked back up to original wiring and it still works. At least I haven't blown anything up yet. Its been fun so far LOL

[Dan Baldwin]

Now I'm confused. I'm not sure what you mean by "nothing happened". The LED either stays on or stays off no matter where you move the stick?

Just to be sure we're on the same page, I wanted for you to leave you servo amp/LED set up EXACTLY as you already had it when it was functioning normall, just add a resistor from one motor output lead to the center-wiper lead of the pot. Do not remove the center pot lead from the board, and do not move either LED connection. If that didn't achieve the desired result, put the resistor from the other motor output lead to the center-wiper lead of the pot. If the resistor stops the system from functioning, try a much larger resistor, such as 100K.

Dan

Congrats Terry

Dan, as usual I'm a bit confused. What I tried so far is I put the 22k resistor in line from one motor lead to the center of the pot and had the led hooked up to the other motor lead and the original pot wire. Nothing happened.

Than I tried swapping motor leads nothing.

Than for kicks and giggles I tried one motor lead to led and the led to the negative on the servo wire, and the 22k inline on the center of the pot. Nothing.

Hooked back up to original wiring and it still works. At least I haven't blown anything up yet. Its been fun so far LOL

[dleroi]

Currently I have to hold the rudder over to the right to keep the lites lit. Releasing the rudder lights go off. Now mind you I am able to keep the lights on by moving the trim lever. Simple enough.

What I am wondering how would one go about using the rudder to flip the lights on, move tthe stick to the right, blip the stick to the left lights go off. Of course using just the existing servo parts as we are now.

Fliboy,

You COULD use a single coil latching relay. This is a relay that you energize by momentarily applying a signal to its coil. Then, it stays energized (latched) until you reverse the signal. In your case, you would connect the coil where the motor was originally connected to the servo board. Moving the stick in one direction would energize the relay. It would stay energized when you returned the stick to center and it would de-energize when you moved the stick the other way.

One that I'm familiar with is 10.6mm x 9mm x 4mm and weighs a gram. Its contacts are rated at 2 amps. It draws 20 mA to energize or de-energize.

- Don

[shanghai_fool]

That would not solve the hysteresis problem. The relay would energize/de-energize with only very slight slick movement from center. I like the positive feedback solution better. I need to hack a servo to test this but I'm working on other problems at the moment. The last time I needed this, I used a PIC.

[dleroi]

That would not solve the hysteresis problem. The relay would energize/de-energize with only very slight slick movement from center. I like the positive feedback solution better. I need to hack a servo to test this but I'm working on other problems at the moment. The last time I needed this, I used a PIC.

But, his problem isn't hysteresis. Rather, that he has to hold the stick over to keep the LED on.

Granted, if he can do it with a single resistor, that will be the better solution. But, a single coil latching relay is just begging to be hooked up to an H-bridge.

The amount of stick movement required will be the same as it is now. If it's too little, maybe he could add some expo?

- Don

[mrfliboy]

Now I'm confused. I'm not sure what you mean by "nothing happened". The LED either stays on or stays off no matter where you move the stick?

Just to be sure we're on the same page, I wanted for you to leave you servo amp/LED set up EXACTLY as you already had it when it was functioning normall, just add a resistor from one motor output lead to the center-wiper lead of the pot. Do not remove the center pot lead from the board, and do not move either LED connection. If that didn't achieve the desired result, put the resistor from the other motor output lead to the center-wiper lead of the pot. If the resistor stops the system from functioning, try a much larger resistor, such as 100K.

Dan


I think I know what you are saying to try tonite. All that will be tried is a 22k resistor added to existing working setup, between one motor lead and the center pot lead. That sure sounds simpler than all I tried yesterday. LOL

Don and Shanghai, great thoughts as well. I am trying to keep this as simple as possible. LOL. In my mind (not very electronic savy) I thought it would need to be a latching relay of some sort.

BTW my goal is landing lites on this one.

http://www.rcgroups.com/forums/showthread.php?t=944359


Alrighty, we tried the 22k resistor on one motor lead and the center pot. It still works the same as before. IE when I move the stick and hold the stick to the right, led lights, release the stick led goes off. Now the pot adjustment is extremely sensitive. Too much and the led stays on, too little and no led. Would there be a reaason to try a larger resistor?

[Dan Baldwin]

Did you try hooking the 22K resistor to the other motor lead to see what would happen?

If the LED now comes on abruptly with no linear region, it sounds like we're on the right track. You might need to use a smaller resistor. I don't think you will want to use anything smaller than about 10K.

Dan

[mrfliboy]

Did you try hooking the 22K resistor to the other motor lead to see what would happen?

If the LED now comes on abruptly with no linear region, it sounds like we're on the right track. You might need to use a smaller resistor. I don't think you will want to use anything smaller than about 10K.

Dan


Yes I tried hooking it to both motor leads, one being the one with the 150ohm resistor in line, the other without the resistor (150). Memory serves me the same occurred. It seems the the brightness was dimmer than before. But movement of the pot made it dimmer and brighter, but sensitive to whether or not it would turn on moving the stick. A little tough to describe but I'm having fun. LOL

[Dan Baldwin]

Yes I tried hooking it to both motor leads, one being the one with the 150ohm resistor in line, the other without the resistor (150). Memory serves me the same occurred. It seems the the brightness was dimmer than before. But movement of the pot made it dimmer and brighter, but sensitive to whether or not it would turn on moving the stick. A little tough to describe but I'm having fun. LOL

So when you moved the 22K resistor to the other motor lead, the stick seemed to brighten and dim the LED instead of turning it on and off? That sounds perfect. Some value of resistor on the lead that made it turn on and off abrubtly should do the job.

Dan

[Stef]

Adding resistors will not change the way the LED turns on or off you'll need at least 1 pn junction. Leave the pot in place or put a mini in place then you can control the travel point that turns it on.

[24vdc]

WOW, I just made a couple of RC switches from servos! I can tell you how! Pm me.

It's easy.

You need

#1 any servo
#2 relay such as NAIS (Panasonic) 10A SPST RELAY, 5 volt coil http://doc.chipfind.ru/pdf/nais/dk1a5v.pdf

solder out the servo motor
connect one servo motor lead to relay coil prong #1
connect the black ground servo wire (there are three red,white, and black) to relay coil prong #2

Now you have a relay switch that can handle up to 10 Amps of current!

-Post up your rc setups at http://rcgearing.com
HoaRC or anyone who knows about this, I tried this and I just can't get it to work. Here's a picture. I checked the radio by plugging a servo in and it works fine on either channel. I checked the servo I used before opening it up and that works. I put a jumper between the circuit prongs and my led lights up (so the led circuit works). I tried it with different wire, a new relay and a different servo. Nothing seems to work. Any ideas?
http://i174.photobucket.com/albums/w83/olvidame/diagram.jpg

[modfly]

I want to switch LED nav lights on and off in flight. The load is about 40mA at 5V
I've heard its possible to do this with a servo amplifier but how ?

Is there a better / lighter way of doing this

Thanks

Terry


I'll post a simple easy way to do this. For 40ma load, you do not need a bulky relay, all you need to do is source current to one side of the load like I did here.....http://www.rcgroups.com/forums/showpost.php?p=10851036&postcount=26


In the above mod, The (+) voltage is connected to one side of the load so that all the servo amp does is supply the (-) voltage to complete the circuit.


here is a video of the servo amp driving two white LED's that are wired in paralell.....http://www.youtube.com/watch?v=gSPUiB2gFBk

[Happy camper]

I bought 20 or so 3mm LEDs with the resistor already installed to operate on 6-12 volts. Will I be able to hook them to some sort of sequencer like this or will I need LEDs without the resistor already installed.

HC

[coriolan]

I want to switch LED nav lights on and off in flight. The load is about 40mA at 5V
I've heard its possible to do this with a servo amplifier but how ?

Is there a better / lighter way of doing this

Thanks

Terry
That circuit works fine and to drive LED you don't even need the mosfet or relay:http://www.uoguelph.ca/~antoon/gadgets/rc-sw.htm
A 330/470 ohms resistor at pin 12 or 13 in serie with the LED is all you need. Output 12 or 13 determine if the LED goes on above or bellow the set point(100K pot) which can be replaced with a fixed resistance for even less weight.
All of that on a small Pc board will weight a lot less than a micro servo

[ElectricRichie]

anyone know how to find out what the max current a servo amp can handle? its only a small Hextronik HXT500 servo. 5 gram.

[HoaRC]

anyone know how to find out what the max current a servo amp can handle? its only a small Hextronik HXT500 servo. 5 gram.

best guess - .5Amps continuous - 1A peak.