142 lines
7.4 KiB
Plaintext
142 lines
7.4 KiB
Plaintext
PrimoPyro1990
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.... Electrical Delays ....
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DISCLAIMER: The following file contains information of harmful or illegal
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nature. Neither the BBS or author providing this information
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can be considered responsible for the use of this file.
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The person using this knowledge is solely responsible for
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it's use or misuse. This file is intended to educate only.
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This file is companion to 2 GIF files. These files are schematics for electr-
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onic delay circuits.
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To produce delays in the ignition or detonation of pyrotechnic
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devices, chemical, electrical, and mechanical devices can be used. In the
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chemical family there are various ways to cause a delay. The foremost is
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probably sulfuric acid and a chlorate. The chlorate is mixed with a combus-
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tible substance and a rubber balloon filled with sulfuric acid is placed in
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the chlorate mixture. Depending on the thickness of the balloon and the
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ambient temperature, the acid will eat through the balloon in anywhere from
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5 mins. to 3 hrs. When the acid contacts the chlorate mix, the mix will catch
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fire. There are other reactions such as silver nitrate/magnesium and water,
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potassium permanganate and glycerin, and sodium peroxide/sawdust and water.
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Mechanical delays are usually a clockwork device that releases a spring
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powered firing pin to detonate a primer. The clockwork can also be used to
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close an electrical circuit to set off a detonator.
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In the electrical family there are many ways to make a delayed ignitor. One
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way which is an electrochemical reaction is to make a delayed battery. This
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device uses a dry battery consisting of alternate pieces of zinc and copper
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sheet metal. This is a battery which only needs an electrolyte to cause a
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current to flow. If you use sulfuric acid as the electrolyte, you can arrange
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a barrier to keep the acid from the battery. When the acid eats through the
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barrier and wets the battery a current will flow which can be used to set off
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a detonator. Each cell (one set of copper/zinc) will produce about 1.5 v.
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You will have to make sure that there is enough surface area in each cell to
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provide enough current (amperage) to trigger the detonator. Any number of
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cells can be wired in parallel to produce enough amps. The problem with this
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delayed battery is it is temperature sensitive. The acid will eat through
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the barrier faster on a hot day than on a cold day.
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A long delay device can be made from a simple relay and a few batteries.
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Wire up a relay to a battery to hold the normally closed contacts open. A
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second set of batteries is then wired to these contacts to supply current for
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a detonator. Since the first set of batteries are holding the contacts open,
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no current flows through the detonator. As soon as the first set of batteries
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loose enough power, the contacts will close and the firing circuit will be
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complete, firing the detonator. An optional resistor can be used to limit the
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current to the relay thus lengthening the delay a bit. Enough current must be
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supplied however to operate the relay. This delay will be found to be sensi-
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tive to shock and vibration as the contacts can be closed prematurely if the
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relay case is tapped too hard. Insert a safety switch in the detonator side
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of the circuit to be thrown after the power to the relay is applied.
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Fig. 1
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This is an electronic delay that can be tailor made for delays from a few
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seconds to a couple of hours. It consists of a 555 IC Timer wired in an
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astable mode to provide clock pulses to a CMOS 4017 Decade Counter/Divider.
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A 555 can be made to provide delays of about 20 mins. after that the sizes
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of the timing capacitor and resistor gets a little large. The 4017 will
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count these pulses and can be used to lengthen the delay.
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Parts list
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------------
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R1 --- this is actually a multi-pole switch wired with a number of different
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resistors so you can dial in the delay you want
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R2 --- 1K ohm 5%
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R3 --- 440 ohm 5%
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C1 --- Timing capacitor - Pick a capacitor to suit the delay you want.
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Typical values are 100 ufd. to 200 ufd.
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C2 --- .001 ufd.
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Q1 --- 2N222 npn - If your load needs more power wire a power transistor
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as a darlington pair.
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IC1 --- 555 IC timer - A CMOS type is available if you want to cut the power
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requirements.
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IC2 --- 4017 CMOS Decade Counter
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SW1 --- SPDT switch
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Breadboard this circuit to understand how it works. That way you can plug in
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different values for the timing circuit to give you the range of delays you
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may want. To use the timer, make sure sw1 is holding pin 15 of IC2 to Vcc.
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This makes sure the counter is reset. Apply power to the timer then throw
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sw1 to put pin 15 at ground potential. Depending on the delay you want, take
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the delay off pins 1 - 12 of IC2. The schematic shows pin 11 as being used.
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When you have adjusted the timer components to give you the delay range you
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want, layout a pc board and mount the components to suit.
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Fig. 2
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A new programmable timer chip has been released. This chip uses less power
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and parts than the 555/4017 device. The chip can be found in Radio Shack for
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about $3.00. It is a LS7210 programmable digital delay timer. By varying a
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resistor/capacitor combination you alter an internal oscillator and set a
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fundamental delay period or LSB. Then by putting any combination of 5 pins
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low, you can choose the delay to be LSB, LSB+2, LSB+1, LSB+3, or MSB. With
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LSB at 1 min. the timer can be made to give delays of 1, 2, 4, 8, or 16 mins.
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By seting pin 8 (16) and pin 11 (2) low, the timer will give a delay of 18
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mins.
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Parts List
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-----------
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IC1 --- LS7210 digital timer
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R1 --- 4.7K Current limiting resistor
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R2 --- Timing resistor - Choose value for appropriate delay
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C1 --- Timing capacitor - "" ""
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SW1 --- SPDT switch - Trigger
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SW2 --- DIP switch - 5 place microswitch to set time delay
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Q1 --- 2N222 npn transistor
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Assemble the circuit on a universal breadboard to get a feel for the circuit
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and to help set the fundemantal delay. You can use 1% metal film resistors
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and a trimming resistor to obtain an accurate delay. Remember to use the same
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power source in the tests as you plan to use in practise as the timer is
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sensitive to voltage changes. You can obtain an LSB of one hour by using a
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47 mfd. capacitor and a resistance of about 70.7 Kohms. If you desire to pre-
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set the delay, use a hard wired connection instead of the microswitch.
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SW1 the trigger, is set to the positive position, the power is then applied,
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and sw1 is thrown to the negative to start the timer.
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An idea to use if you want the timer to self-destruct. Wire the delay point
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to point without using any sort of pcboard or any other type of board. Use
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solid wire to lend the delay some support. Then in a suitable container, put
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an appropriate amount of PBX. This is Plastic Bonded Explosive. It is made by
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mixing 85% PETN and 15% Polystyrene plastic. The mixture is wet down with
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acetone to blend the ingredients properly. While the explosive is still wet,
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insert the delay into the PBX and let it harden. Use the detonator from the
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delay to set off the PBX which in turn can set off your main charge. The PBX
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will vaporize most of the delay.
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*** Kilroy was here ***
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