Need inexpensive 6 pad lpr controller.

[George Rachor]

Oregon Rocketry had a low power launch today at Garden Home Park near Washington square. We had a good turnout that included a cub scout group. W even had reasonable weather and calm winds for most of the session.
We had a huge number of misfires. While some were due to igniter failures with first time users we had a major problem with a pretty old six-pad controller. Powered by a Car Jump starter battery it sure seemed current limited. I'll troubleshoot the existing controller but would be interested in what other clubs were doing. What controllers exist to day that will support at least a 6 pad rack?

 

[rharshberger]

Oregon Rocketry had a low power launch today at Garden Home Park near Washington square. We had a good turnout that included a cub scout group. W even had reasonable weather and calm winds for most of the session.
We had a huge number of misfires. While some were due to igniter failures with first time users we had a major problem with a pretty old six-pad controller. Powered by a Car Jump starter battery it sure seemed current limited. I'll troubleshoot the existing controller but would be interested in what other clubs were doing. What controllers exist to day that will support at least a 6 pad rack?

was yours an old Pratt?

 

[Voyager1]

Oregon Rocketry had a low power launch today at Garden Home Park near Washington square. We had a good turnout that included a cub scout group. W even had reasonable weather and calm winds for most of the session.
We had a huge number of misfires. While some were due to igniter failures with first time users we had a major problem with a pretty old six-pad controller. Powered by a Car Jump starter battery it sure seemed current limited. I'll troubleshoot the existing controller but would be interested in what other clubs were doing. What controllers exist to day that will support at least a 6 pad rack?

For a basic wired controller, the main problems would be

1. Battery
2. Internal wiring and switches
3. Field cables
4. Ignitor clips

1. Is the battery appropriate for the job? Is it in good condition and charge state? For a 6 channel launch that you describe, a car battery, or equivalent, should be more than adequate. Even a 12V 7Ah SLA battery should be fine for a days' launching.
2. The wiring and switches in a simple wired controller are subject to bad connections, solder joints, or mechanical damage. They switches might not be rated for the ignition currents experienced and might degrade through arcing.
3. The field cables you use out to the pads should be a reasonably heavy gauge, say 14 AWG or heavier, to reduce the cable resistance to the ignitors. You want most of your battery voltage dumped over the igniters, not the field cable, providing more igniter current.
4. Igniter clips get corroded very quickly from frequently being blasted by motor exhaust. Keep the clips away from the motor exhaust and keep them clean. Unfortunately, most low power igniters are very fragile and are also prone to short-circuiting due to poor installation.

You are better off going for a relay-based launch controller. Many clubs are opting for these systems that are either wired or wireless. However, these systems are not cheap, but they are worth the expense. These systems are very flexible and can be added to as the requirements change. There are at least two vendors of these systems that come to mind: Wilson F/X and Altus Metrum.

If you posted some more details of your existing system with pictures (inside and out), we could probably help you troubleshoot it.

 

[rharshberger]

1. Is the battery appropriate for the job? Is it in good condition and charge state? For a 6 channel launch that you describe, a car battery, or equivalent, should be more than adequate. Even a 12V 7Ah SLA battery should be fine for a days' launching.

We have found that a 6V battery works better with the Estes igniters, the 12V car batteries we were using was burning the wire instantly, since switching to a 6V SLA the success rate with Estes igniters has gone up significantly.

 

[Handeman]

We had a couple of the Pratt 6 pad controllers. They worked well until they didn't. Most issues were with clips and external wires, but eventually the safety key connection got flakey and the internals were not dependable, although it is hard to tell if it is the external wires or clips. We never had issues with the 12V lawn mower battery. We've kept the Pratt controllers as emergency backup.

We built a new controller in 2017 in a Kobalt 19" tool box and put 4 quad outlets on the back so it's an 8 pad box now. We use 50 ft. 16 ga extension cords out to the pads and then about 6 ft. clip whips (clips on the end of a lamp cord) that plug into the extension cords. We have a 5 rod sawhorse, but only use 4 rods for Estes sized rockets along with 3 1010 rails and a 1/4" rod for E- G motors since we have so many TARC teams showing up in the winter/spring time.

It's been in use for six seasons and about +16 launch days a season and no issues with the controller. The clips, take a fair amount of maintenance. Always keep a few good spares on hand.

I think this is the last version of the schematic we used.

We used the relays because early versions were having issues with the continuity LEDs lighting when the pad switch for other pads were turned on.
The ARM and Launch buttons are 2.5" diameter lighted momentary buttons on opposite ends of the controller. That means it is a two handed control to actually launch. It also allows the LCO to let the kits push the launch button on their own rocket while still having positive control of the ARM switch. We've had a few young ones push the button as soon as the countdown started.

The circuit breaker is a resettable 30 Amp, that has never tripped. The Power switch is an ignition key switch good for 100 amps and the key only comes out when off. The relays are 12V 40Amp Automotive types. The Pad switches are HD toggles and internal power is 16ga wire. The LEDs are Ultra-Bright so they are easy to see in bright sunshine.

The cost, including a tool box and aluminum plate for controls was about $140 back in 2017.

 

[sghioto]

Here's my entry into a 6 pad relay controller.
Normally it is a 5 pad system using a standard 8 conductor Cat5 cable with 8 pin connectors.
To get 6 pads wired directly without getting fancy requires 9 conductors or 8 conductors using a separate small battery in the Control Panel.
Cat5e with a ground wire is an option. Different options depending on what cable might be available.
In this system each pad is selected by closing a relay contact to connect the igniter to the master firing switch SSR 60A, a 60 amp solid state relay.
This allows any combination of pads to be setup for drag racing with no arcing of relay contacts.
Total cost under 200.00 or less depending on components on hand.