Elenco Nerve Tester User Manual

NERVE TESTER KIT

MODEL K-20

Assembly and Instruction Manual

Copyright © 2010, 1989 by ELENCO®All rights reserved. Revised 2010 REV-H 753220

No part of this book shall be reproduced by any means; electronic, photocopying, or otherwise without written permission from the publisher.

ELENCO

®

PARTS LIST

If you are a student, and any parts are missing or damaged, please see instructor or bookstore.
If you purchased this nerve tester kit from a distributor, catalog, etc., please contact ELENCO

®

(address/phone/e-mail is at the back of this manual) for additional assistance, if needed.

Parts Verification

Before beginning the assembly process, familiarize yourself with the components and this instruction book.
Verify that all of the parts are present. This is best done by checking off each item in the box provided next to
the part in the parts list.

RESISTORS

Qty. Symbol Description Color Code Part #

r 1 R1 470Ω 5% 1/4W yellow-violet-brown-gold 134700
r 1 R2 47kΩ 5% 1/4W yellow-violet-orange-gold 154700

SEMICONDUCTORS

Qty. Symbol Description Part #

r 1 SCR1 SCR C106B 319106
r 1 D1 Diode LED red 350002

MISCELLANEOUS

Qty. Symbol Description Part #

r 1 T1 Transformer 442100
r 1 P1 Double Sided PC Board 510320
r 1 PC Board 518020
r 1 S1 Switch Push Button 540100
r 1 S2 Switch Slide 541102
r 1 Solder Roll 24” 551124
r 1 B1 Battery Snap 590098
r 2 Wire 9” 814920
r 1 H1 Wire 9” Bare 845000

-1-

Resistor Transistor

PARTS IDENTIFICATION

Battery Snap

LEDSwitches

SCR

Slide

Push Button

Transformer

IDENTIFYING RESISTOR VALUES

Use the following information as a guide in
properly identifying the value of resistors.

BANDS

1

2 Multiplier Tolerance

PC Board

Double Sided

PC Board

OR

• Do not short circuit the battery
terminals.

• Never throw batteries in a fire
or attempt to open its outer
casing.

• Use only 9V type, alkaline
battery (not included).

• Insert battery with correct
polarity.

• Do not mix alkaline, standard
(carbon-zinc), or rechargeable
(nickel-cadmium) batteries.

• Non-rechargeable batteries
should not be recharged.
Rechargeable batteries should
only be charged under adult
supervision, and should not be
recharged while in the product.

• Remove the battery when it is
used up.

• Batteries are harmful if
swallowed, so keep away from
small children.

Batteries:

-2-

INTRODUCTION

Test your nerve with the Nerve Tester Kit. It takes a steady hand, should you touch the twisted wire with the
probe, a slight electrical shock will be felt. The shock is very weak and harmless. For the weak of heart or
“chickens” a switch removes the electrical shock and substitutes a Light Emitting Diode (LED) which lights up
when the probe touches the wire.

THEORY OF OPERATION

The circuit of the Nerve Tester is shown on page 6 of this manual. The circuit consists of two basic circuits. One
is the high voltage generator and the other the LED with its latch circuit. We shall study each circuit further.

THE LED CIRCUIT

Figure 1 shows the basic LED circuit. Note that the battery is placed in a
series circuit with resistor R1, the LED and the Silicon Controlled Rectifier
(SCR). The positive voltage of the battery is placed on the anode of the SCR.
The negative voltage is connected to the cathode. Under these conditions if
a positive voltage is placed on the gate of the SCR, even for a 1/1000 of a
second, the SCR will conduct current and keep conducting when the positive
voltage is removed from the gate. This will keep the LED lit until the voltage
is removed from the SCR. This is done by closing switch 1, which shorts out
the SCR. Resistors R1 and R2 are needed to limit the current in the LED and
SCR.

THE SHOCKER GENERATOR

Figure 2 shows the basic circuit used to produce the high voltage of the
shocker generator. The heart of this circuit is the transformer. We shall review
the operation of a transformer to understand the circuit.

A transformer has two or more windings around an iron core. If a changing
current is placed in one of the windings, it will appear in the other winding.
The voltage across the second winding will be the ratio of the turns of the
transformer. If the first winding has 100 turns and the second has 1,000 turns
(10:1 ratio) the secondary voltage will be 10 times the primary voltage. In our
transformer, the ratio is 30:1. Therefore, the 9V battery voltage will be
stepped up to 270V on the secondary.

The primary wire of the transformer is connected to the negative side of the battery. The positive side of the
battery is connected to the twisted wire. The other primary wire is connected to the probe. When the probe
touches the twisted wire, a DC current flows through the primary of the transformer. The secondary of the
transformer will only have voltage the instant the probe touches the twisted wire and the instant the probe leaves
the wire. Again, only when the current changes. Refer to Figure 3 and note that there are two voltage spikes
for each time the probe touches the twisted wire. This is because the current changes twice.

Note that the probe is double-sided copper with an insulation in between. One side is negative (ground), the
other side connects to the high voltage. Your hand touches both plates and therefore you feel the shock.

LED

R1

S1

Cathode

Gate

Anode

SCR

Wire

Probe

R2

Figure 1

T1

S2

Wire

Probe

Figure 2

Figure 3

Current in

Primary

Voltage in

Secondary

+270

–270

Max

Zero