# New guy, needs opinions

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#### Dwight

##### Active Member
hello there,

I am just now getting back into rocketry ( was flying Estes Models as a kid )

I built a launch pad and a hand held launcher, am about to graduate to mid power and decided to build a launcher that I wont have to replace later when I get into high power.

Part of the fun for me is to build the whole thing myself.

Here is a schematic for a simple but I think effective launcher.

Could those that know better comment on it please. ( I dont care about spell checking )

( I may replace the two yellow LED's with buzzers, and I realize that I will have to play around with the resistances of the R1 and R2 resistors )

I am just curious is the general plan is sound, and if there are any other suggestions.

( you will notice that I have no electronics experience at all )

#### DavRedf

##### Well-Known Member
Looks fine to me though you might want to use a car relay instead of the solenoid.
The resistors will need to be about 680ohms in this circuit depending on the led's.
For the controller to ignighter leads I use hobby welder cable as it is more flexible tha standard cable and it takes the current with no loss.
Hope this is of some help.
David

#### Dwight

##### Active Member
ACK!

Just found the first error,

No saftey key at the hand controler..... ok this is added.

welcome to TRF

#### Micromeister

##### Micro Craftman/ClusterNut
TRF Lifetime Supporter
TRF Supporter
welcome to TFR here the diagram for the relay launcher I've been using for a very long time

#### bobkrech

##### Well-Known Member
I particularly like Carl Tulanko's controller http://www.rocketryforum.com/reviews/12vlauncherschematic.jpg
from the thread http://www.rocketryforum.com/showthread.php?threadid=5303&highlight=circuit referenced above.

It's very similar to yours, but has a few extra features worth mentioning.

1. The continuity at the pad is simply a piezo buzzer so you don't need to look at an led. This buzzer also is activated when the pad is armed so that anyone in the vicinity know the pad is hot.

2. It has a test light to check if the launch relay is welded shut. A nice safety feature.

3. The hand control unit has 3 leds for power, continuity and arm which are the 3 important things you need to know.

4. I don't think a switch for the hand controller continuity check is necessary or desirabe and this controller doesn't use one.

A great place to buy launcher components is from http://www.allelectronics.com/ Shipping is only $6.50 for any order which is a true bargin. They sell 40 amp automotive relays for ~$2.25 and prewired sockets for about $2. http://www.allelectronics.com/cgi-bin/category.cgi?category=500700&item=RLY-631&type=store http://www.allelectronics.com/cgi-bin/category.cgi?category=525&item=SRLY-2&type=store Batteries and chargers are also really cheap. The 7 AH or the 12 AH gell lead acid batteries for$22 and $25 are a common choice. http://www.allelectronics.com/cgi-bin/category.cgi?category=160400&type=store This 14 volt wall wart power supply would make a pretty good 12 volt battery charger for$3.50

http://www.allelectronics.com/cgi-bin/category.cgi?category=815&item=DCTX-1436&type=store

Another great source of batteries is http://www.batteryspace.com/store.asp You can't beat their prices for NiMH cells and packs. Specials are outrageous.

Good luck.

Bob Krech