Never going to lawn dart again

Over the Labor day weekend I had a grand time out at Freedomfest, but one bad delay charge turned hours of work into a pile of recycling scraps. On Monday I was putting up a new garage door opener and got to thinking about the handheld remotes and rockets.

Long story short I did some searching and found a single channel remote controlled relay with a 1000 meter range. I am thinking of bundling the battery, receiver, ejection charge and ematch in a compact box I can hang on the shock cord and be able to pop the nose cone off in case of a failed ejection charge or even one that is just a little late.

https://www.ebay.com/itm/12V-1CH-10...ion_Controls_Touchscreens&hash=item58a1cd4a9d

darn things are only $8.50 each. I ordered 2 and will test on the ground before trying to fly.

These sell those thing $ 50 from China, $ 8 from US, I find it suspicious

It's basically a garage door tx/rx switch. I would be a little suspicious of the claimed range, but for $8.50 it's worth playing with. You can have it pop open a trap door and drop a paratrooper to test it... sounds like fun!

I hate to be the cold water on a great idea, but I have to mention that my dust collector in my shop has a remote switch that uses the same concept and frequency as the garage door openers, and it turns on all the time on its own. Might want to rethink that, it would be a shame to have a ejection charge go off in your hand when your neighbor opens his garage. Or at least work out a safety switch.


TA

I had a similar one a while back - while the frequency is set, there was a set of jumper pads on both the remote and receiver units that let you set your "code" by soldering or cutting the link between the pads.

Never had an issue - the other thing to remember is that you're going to be a long way from houses and garage doors

On a slightly different angle, one of the members in our club has a radio link that he can send DTMF tones over - he uses a sequence to trigger his recovery if he needs to do it manually.

Krusty

I have played with these types of cheap wireless relay boards a fair bit, including as part of a hybrid fill system. One thing that you must be very wary of is the advertised range. In my experience, while on the odd occasion, you may get the relay to trigger at a range of 1000m, in reality they only work reliably at distances of <100m. To use one to trigger an event in a rocket, you would be asking for trouble.

I have wondered why no one has used RC radio gear for this purpose. Reliable, long range, [as in miles] can be failsafed, reasonable cost. [~$50-80] Some can provide altitude telemetry and work as a model locator too.


Richard

I absolutely agree with the concept!
Flipping a switch that triggers a backup event seems much more productive than shouting "Come on - COME ON !!! eject eject eject - aaaahhhhhHHHH!!!!!!" -splat.

Seems to happen way to often - Happened to me last July. (Before and After pictures below)

-A "remove before flight" type of lockout would be prudent.
-Need to make sure that G-forces encountered in flight would not inadvertently trip the switch.
-Size is a factor, will this fit in a BT80 or 2.6" tube? Once you start to exceed 3 inches, ebays' and dual deploy start becoming more common.

At $8.50 you can afford to experiment. I'd probably pay up to 10x times that amount for a SMALL, RELIABLE system that could easily be moved from rocket to rocket.

Got the Remotes and Relays in the Mail on Thursday. Going to stop by Walmart and pick up a 12V battery so I can power them up and test the Distance. The plan is to rig a E-Match to the relay and have it sitting in the Driveway. I will Drive down the road, turn around and drive back holding the button I will have my son on the phone and he will tell me when the match burns. We will measure from there.

Mechanical relays in a rocket doesn't sound like a good idea. Switch bounce is not your friend. Solid state relays or fets will be smaller and more reliable.

I worked out a wireless system like this as part of the complicated recovery process. Spread spectrum R/C radios are perfect for this as the receivers are small, the signals aren't likely to jam and they're easy to use but the range can be an issue. The solution I found was a 433MHz Thomas Scherrer add on module for RC gear. I bought the transmitter, 5W booster and long range receiver. This system has a range of upwards of 5 miles. Then I bought a PWM controlled relay module from Pololu that plugged into the receiver to fire the igniter. It's not a cheap system but it worked. I already had a Spektrum DX8 so I just had to buy the Thomas Scherrer stuff for about $800.

https://www.dronesvision.net/en/lon...pv-system-tslrs-tx-rc-transmitter-v6-pro.html

RochonRockets said:

Got the Remotes and Relays in the Mail on Thursday. Going to stop by Walmart and pick up a 12V battery so I can power them up and test the Distance. The plan is to rig a E-Match to the relay and have it sitting in the Driveway. I will Drive down the road, turn around and drive back holding the button I will have my son on the phone and he will tell me when the match burns. We will measure from there.

Click to expand...

How about having a pair of video camera's and a light... both videos are synchronized with a control light or clap board, then when you drive the one in the car will record your remote activation, and the other will give you an exact time when the E-Match fires (or a light turns on - benefit: it's cheaper than burning up your E-Matches). Much safer than driving while using a cell phone, and you can confirm your distance and reaction times repeatedly and accurate down to the frame. I'd also recommend using a bicycle with a bike computer... those are extremely accurate (down to a hundredth of a mile, vs a car's tenth of a mile).

K'tesh-I like the light idea. The car is equipped with a nice hands free system for the call so no danger there. I also have a hand held GPS so I should get within feet of the distance.

BotScott-This is something SUPER cheap to give me something to do other than mutter "pop" repeatedly when the rocket is falling.

Ok got back to late to test tonight, but I did get it wired up for test and will make a battery holder tomorrow. If I use the case it came in the size is 2x1.75X.75 inches plus the battery holder.

with the project box it is 4x2x1 inches but will have the batteries inside. I plan on using 2 batteries in parallel to give it extra amps. Will test tomorrow if the schedule permits.

Ok I made a little battery holder and wired it in, Also picked up a LIPO battery to use as the power source to ignite the ematches. Still waiting on the charger for the battery but I have a good plan for safety and power switches.

Ok first round of Range testing is done. Got good reception at a quarter mile through the neighborhood. In clear space it would get even better range. I am building a directionalizer to put around the control antenna, that should double or triple the range. I can't wait to try it out in the open field at Orangeburg. Will test with just the relay click and light in the open field where we have a little over a mile of clear space before using it with a ejection charge.

By the way it is digitally signed so the chances of some other device setting it off are super slim.

Here are some pictures of the Range extending device. Note the professional use of aluminum foil!!

Any serious RSO will not let you launch something base on a mechanical relay; vibrations, G Force can trigger the charge.

Area66 said:

Any serious RSO will not let you launch something base on a mechanical relay; vibrations, G Force can trigger the charge.

Click to expand...

Mechanical relays and cut wires can be a safety issue.

Ok, so I will replace the mechanical relay with a solid state relay. I have a soldering iron and solder.

It is a last resort/everything else failed device.

Late or no deployment is bad but so is very early deployment and you might be increasing the risk of that. My first L2 attempt included an early version of a RC back up unit plus two altimeters . The drogue deployed just after burn out. The altimeter data and video from a forward looking video camera proved the RC unit fired on its own and later testing showed that in 3 out of 50 times that the unit lost signal and then reacquired it would fire a channel. Mechanical relays under g forces might do the same and could not be tested . Just offering my experience .

robertv2 said:

Late or no deployment is bad but so is very early deployment and you might be increasing the risk of that. My first L2 attempt included an early version of a RC back up unit plus two altimeters . The drogue deployed just after burn out. The altimeter data and video from a forward looking video camera proved the RC unit fired on its own and later testing showed that in 3 out of 50 times that the unit lost signal and then reacquired it would fire a channel. Mechanical relays under g forces might do the same and could not be tested . Just offering my experience .

Click to expand...

Good receivers these days have a programmable fail safe mode. You can program a fail safe position for each channel's output in the event of signal loss.

RochonRockets said:

Here are some pictures of the Range extending device. Note the professional use of aluminum foil!!

Click to expand...

Throughly test that 'range extending device'. Some reflectors can decrease the range if not properly designed. Use a buddy and move the antenna up/down and side to side looking for null areas or weird radiation patterns. Hope it works out.


Richard

What frequencies does this device use? There are restrictions as to which frequencies can be used "On the ground" vs in model rockets that can get you in a lot of trouble with the FAA/FCC if the device you use is not permitted.

It is my understanding that ALL radios that perform any flight functions must have operating frequency in the 27, 50, 53, or 72 megahertz band.
Use of 75 megahertz for flight functions is specifically not permitted.

It's most likely on 315 MHz, that's an "open" band with a very low power output restricted to periodic transmissions: those that you initiate by pressing a button or something like that. They are very commonly used for garage door openers, remote light switches, etc. It will be interesting to see how much range he can wring out of this. The parabolic transmitter antenna might be an FCC issue... I'd look it up before using it.

It is a 315 MHz radio. I doubt I will need the parabolic antenna in open air. The solid state relays arrived yesterday and I will be swapping those out after bench testing sometime this week. The one I have is a click on/click off relay. I have another coming that is momentary so the relay passes current only while the button is held down.

I got the mechanical relay removed and the solid state relay installed. While I was at it I put the LIPO battery connection in line with the relay output with a connector to allow easy changing on the battery. I am still waiting on the battery holders for the A23 battery that powers the board. All in all it is done and I have burned 2 Estes igniters with it and waiting on my son to get home from school before testing with a full scale igniter and some black powder. Not real happy with the momentary action but the click on/click off works well. As soon as the rocket comes into range of the signal of the button being held down it will lock on and fire the igniter. I have to click another button to turn the voltage off.

It is a learning relay, so I had to push a button on the board and then push the button on the remote to link them.

I have several similar receivers and they work well with a 3s LiPo. There's no need for 2 separate batteries.
The receiver I like is this one
https://www.ebay.com/itm/281114817866

It has momentary contacts so the relay is closed only as long as the transmitter button is pushed.

This one can be set to use momentary but the Solid state relay does not like it. The voltage and current fluctuate for about 10 seconds before Rising to the full 8.3 Volts.