Eggtimer TRS switches

[BradMilkomeda]

I successful assembled an Eggtimer TRS in the spring and just now trying to integrate it for the fall when the crops are freed from the flying field.

I am curious how everyone is integrating a switch into the system. I’ve read the manual and there are a lot of options.

The basic one, following the recommendations in the manual, seems to use one battery and switch the power for deployment while keeping the power constant to the GPS and micro controller. The downside to this approach is that it requires the Eggfinder LCD to connect and to activate the launch process. If the LCD gets powered down, disconnected or in another bad state there is no way to reset the micro controller without disassembling the avionics bay to disconnect the battery. There does not appear to be a way to reconnect the LCD without resetting the micro controller. This leads me to believe that it nescesary to have a switch connected to the reset pins.

It seems like a single DPDT switch could be wired so that in the off sate, reset is closed while the deployment is open, and in the on state reset is open and the deployment battery is closed. I have been trusting screw switches and twist and tape, but I’m not sure I’d trust a slide switch not to bounce, which would be catostrophic on the reset connection.

I still need to do the experiments to determine if the controller will go to the ready for launch state if the GPS has not locked, either explicitly from the LCD or by itself after it has passed the search for the LCD and terminal. This could be implemented with just one switch one the power for everyone. The problem here is that in the LCD menu does not indicate when the GPS has locked on to the satellites.

 

[Keisling]

I have mine wired 2 batteries and 2 switches. I power the altimeter and pair it before going to the pad. I only switch the deployment side battery on once it's on the pad and ready for flight.

 

[Eric]

I have a couple TRS units. The one I currently have mounted for a nosecone mount. This setup survived a K2050 in the Nike Smoke drag race at LDRS.



I soldered up a Y harness to run both sides off of one battery. The positive lead goes through a push button switch .



I power everything up at my prep table and get a fix. Power it down and finish assembling the rocket. Power it up once I'm on the rail. Take a minute or two maybe to get a fix again. That time is spent getting my ignitor up in the motor, amd taking a picture of the rocket on the pad.

Then I start a flight with the LCD controller. Then connect the ignitor leads and check continuity.

With a larger LiPo battery I never felt the need to run two batteries. There is plenty of time at the pad for it to get a new GPS fix. And you can start a flight before it has that fix. And the altimeter will work even if your fix never acquires.

I use the push button switch I had on hand and it worked. But I would not object to replacing it with a screw switch.

 

[BDB]

I use two batteries and one switch for the 9V deployment battery. The OP is right...that means I have to disassemble the AV bay every time I want to turn the GPS on and off. It’s a total PIA. I really need to invest some time to remaking my TRS sled to have two switches. (Though a DPDT switch would be an interesting option.).

 

[dvdsnyd]

I use a single larger battery to power the TRS and deploy the charges.
I created a harness that when the battery is plugged in it powers up the TRS(I plug this battery in at my prep table before going out to launch), but does not put power to the deployment terminal on the TRS. I use a screw switch at the pad to put power to the deployment side. Like others have said, this done mean disassembly of the rocket/av bay is required to turn the TRS off. I have not run into this being much of a problem. A second switch might be nice, but I don't like that it creates another failure point in the system. Nothing is without its opportunity costs.

I would not trust any type of slide switch. I really like the screw switches. If you can mount them securely, you can get a good tight connection that is very robust to flight forces.

 

[cerving]

The TRS will arm for flight even if you do not have a GPS lock, it doesn't know about the state of the GPS. I would have liked to add that feature, but there simply isn't enough space in the firmware for it. I recommend that you put a switch on the deployment power only, do not switch the altimeter power; by doing that, you "safe" the outputs but keep power to the GPS. By the time you connect the power on your worktable, button it up, get it through RSO/LCO, and rack it up, the GPS should be locked. If it's not locked by then, you probably have a problem somewhere.

 

[BradMilkomeda]

For this to work you must also connect and keep the LCD receiver on. If the receiver is powered down is there a way to reconnect in pre-flight mode or otherwise put the TRS into flight mode? It will not automatically go into flight mode when the deployment is powered?

The TRS will arm for flight even if you do not have a GPS lock, it doesn't know about the state of the GPS. I would have liked to add that feature, but there simply isn't enough space in the firmware for it. I recommend that you put a switch on the deployment power only, do not switch the altimeter power; by doing that, you "safe" the outputs but keep power to the GPS. By the time you connect the power on your worktable, button it up, get it through RSO/LCO, and rack it up, the GPS should be locked. If it's not locked by then, you probably have a problem somewhere.

 

[ksaves2]

I have a 38mm rocket with a TRS in a long ebay with the antenna jutting up into the NC where I cut off the bottom of the shoulder. I use a cutter on the main. With a 1300mah 2S battery it can wait on the pad for a very.....long.....time
safely. I too use a Y-harness for power and pyro. I did put a screw switch on the pyro side it case some jerk asks but there is not room for a power switch. I test the night before with bare ematches to make sure nothing blows.
I put charges in and when ready to fly, I simply plug in the battery (wrap the connector with tape) and seal up the ebay. In standby mode the receiver gives the unobtrusive "I am alive beep". No on/off switch. When on the pad. I arm the pyro switch and activate the TRS and go through the start up cycle. It's good to use a checklist and I do practice with arming a TRS with LEDS attached to re-familiarize myself with the process if I haven't flown with it in a long time. (I got 3 of them and
usually one is on the bench outside of a rocket so I can use it to practice on.)

On a minimum diameter Quantum ship, I test the night before, add the live charges, when ready to fly, plug in the battery and secure the connector and go to the pad.

Some folks have ranted about a perfectly good altimeter (Not an Egg product mind you) having a FET failure and blowing on the pad when the switch is turned on, after the previous flight was nominal.
I test with live contained ematches the night before to avoid that possibility entirely. I've plugged in Egg deployment products without intervening switches without issue.

Now, don't try that on an L3 project as to please most overseers one will need to use mechanical switches. Usually, most rockets are larger so no problem with fitting switches in. Kurt

 

[cerving]

For this to work you must also connect and keep the LCD receiver on. If the receiver is powered down is there a way to reconnect in pre-flight mode or otherwise put the TRS into flight mode? It will not automatically go into flight mode when the deployment is powered?

You can't arm the TRS until you power up the deployments, but you should have a GPS fix by that time.

 

[BDB]

The PIA for me was deployment charge testing. If I wasn’t happy with the first test, I had to take the whole thing apart to turn it off before attaching the new charge. Maybe I didn’t have to, but I didn’t want to attach a BP charge to an altimeter that was powered, even if there was a switch on the deployment charge. So I just opened the AV-bay up each time.

I guess the same could be said for deployment charge testing with a Quantum. I just haven’t had to do that with them yet.

 

[cerving]

Yup, that's by design in the TRS. We COULD make it go back to the menu... any input that TRS users can give me on this would be appreciated. Since one leg of the igniter is "live" (just like it is on just about every other altimeter except the Quantum) it's safer to have it go into a state that requires you to power off to reset.

The Quantum goes back to the testing menu after firing, because of its dual-switched architicture the deployment power is essentially off after firing. The only current going through the channels is about 1/2 mA for continuity checking. You can hook up a live charge with it in this state... it's no different than having a separate electronic switch on the power. (Yes, I'm expecting some pushback on this...)

 

[rkaplan]

Looking for suggested wire connections for a Eggtimer TRS and Wifi Mini switch? Thinking of using 2s LiPo for the Wifi to TRS power and 9V for the deployment side.