A WIRELESS THROTTLE

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	THROTTLE2

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This handy motor board simulated a running train and computer connection during the development and assembly of the throttle. Using this gave a much more realistic and practical proof that everything worked the way it was supposed to and to make final adjustments before installation. Note the LEDs to the right used to test the auxiliary computer connections. Back to Index

PARTS LISTS - Almost all parts shown here may be obtained from Digi-Key

or second-sourced from other vendors.

Key	Source	Website	Description
D	DigiKey	http://www.digikey.com/	Source for almost all parts for this project
L	Linx Technologies	http://www.linxtechnologies.com/	Vendor of RF modules and parts
R	Reynolds Electronics	http://www.rentron.com/index.html	Source for RF parts and kits
J	Jameco	http://www.jameco.com/	Assorted bargain parts and tools

Handheld transmitter

PART	Source	Source #	Description	Use
B1	D	N705-ND	9v NiMH rechargeable battery	Main power
IC-1	R	CIP-8E	20-pin 8-bit encoder	Channel selector
IC-2	D	78L05ACZNS-ND	5v @ 100ma voltage regulator TO-92	Low power regulator
ANT	D	ANT-315-HETH-ND	Coil Antenna	Transmit signal
TX-1	D	TXM-315-LC-ND	Transmitter Module	Form signal for transmission
C1	D	P969-ND	47 µfd @ 10v Capacitor	Filter
C2	D	P966-ND	10 µfd @ 10v capacitor	Filter
SW9	D	EG1901-ND	SPDT slide switch	Power on/off switch
D1-D16	D	1N014BCT-NT	Small switching diode DO-35	Isolation
R1	D	150QBK-ND	150 ohm @ 1/2w carbon resister	Battery protection
R2	D	560EBK-ND	560 ohm @ 1/8w carbon film resister	Voltage Drop
R3	D	770-101-R100KP-ND	9 x 100k resister network, common bus	Pull down to zero
SW1-8	D	EG1821-ND	12mm square Tactile switch	Function control
SW1-8	D	EG1080-ND	Key Cap	See catalogue for colors
J1-J4	D		Jumpers	Device selection code

Throttle (Receiver)

ANT	D	ANT-315-HETH-ND	Coil Antenna		Receive signal
RX-1	D	RXM-315-LC-ND	LINX Receiver Module		Tune signal for decoder
IC-1,2	D	296-1391-5-ND	LM324 Quad Operational Amplifier		Condition signals from decoder
IC-3	R	CIP-8D	20-pin 8-bit decoder		Split signal into 8 channels
IC-4	D	160-1364-5-ND	LTV846 4-channel Opto-Isolator		Computer interface
IC-5	D	78L05ACZNS-ND	5v @ 100ma voltage regulator TO-92		Receiver power supply
C2	D	P4669-ND	.33 µfd capacitor		voltage filter
C3	D	P969-ND	47 µfd @ 16v capacitor		Voltage filter
C1	D	P966-ND	10 µfd @ 10v capacitor		Filter
C4	D	399-4264-ND	.1 µfd disk		Local transients
D1,2,3	D	1N014BCT-NT	1N014 Small signal diode DO-35		Filter polarity
R1	D	330KEBK-NT	330 ohm @ 1/8w carbon film resister		Voltage drop
R2	D	470KEBK-NT	470K @ 1/6w carbon film resister
R3	D	68KEBK-NT	68K @ 1/6w carbon film resister
R7	D	33KEBK-NT	33k @ 1/6w carbon film resister
R8	D	62J2893	680 x 5 resister array
R9	D	32K9620	1.5K x 9 resister array
T1	D	2N3904FS-ND	2N3904 small signal NPN transistor
J1-J4	D		Jumpers		Device selection code
R4	D	The value of these parts will vary depending On the running characteristics desired. The following values are one possible combination		2.2K 15K 47K	Panic stop
R5	D				Service brake
R6	D				Acceleration

Throttle (Control)

D-1	D	KBPC110-ND	3-amp Bridge Rectifier	Power Supply, DC
D-2,3	D	1N014BCT-NT	1N014 Small signal diode DO-35	Pulse Generator
D5	D	1N014BCT-NT	1N014 Small signal diode DO-35	Mix Pulse strength
D-6,7	D	1N014BCT-NT	1N014 Small signal diode DO-35	Reverse Lockout
D-8,9	D	1N014BCT-NT	1N014 Small signal diode DO-35	Anti-surge, relay
C-1,2	D	P4671-ND	.47 µfd @ 50v Metallic Film Capacitor	Anti-surge, relay
C-3	D	P5169-ND	1000 µfd @ 35v Electrolytic capacitor	Power Supply, Filter
C-4	D	P5155-ND	470 µfd @ 16v Electrolytic capacitor	Momentum
C-5	D	P4671-ND	.47 µfd @ 50v Metallic Film Capacitor	Pulse Timing U2-B
C-6	D	P1280-ND	10 µfd bipolar capacitor	Spike suppression
U-1	D	296-1391-5-ND	LM324 Quad Operational Amplifier	Reversing Control
U-2	D	296-1391-5-ND	LM324 Quad Operational Amplifier	Wave Shaping
Q-1	D	2N3904FS-ND	2N3904 transistor	Adjust Cutoff point
Q-2,3	D	2N3904FS-ND	2N3904 transistor	Relay control
Q-4	D	497-2539-5-ND	TIP120 NPN Darlington transistor	Power amplifier
K-1,2	D	Z221-ND	12v @ 10amp SPDT relay	Reversing control
LED-1	D		LED	Cutoff point adjust
R-1	D	10KEBK-NT	10k @ 1/8 carbon film register1	Cutoff adjust
R-2	D	U262R254B-ND	250K potentiometer Violet	Frequency
R-3	D	U262R504B-ND	500K potentiometer Brown	Strength
R-4	D	U262R105B-ND	1M potentiometer Lt Blue	Duty cycle
R-5	D	U262R503B-ND	50K potentiometer Orange	Reverse lock
R-6	D	U262R103B-ND	10K potentiometer White	Cutoff point
R-7	D	1KEBK-NT	1k @ 1/8 w carbon film resister	Cutoff current limit, LED
R-8	D	150H-ND	150 ohm @ 1/2w resister	Protection from relay coil
R-9	D	OF102JE-ND	1K @ 1/2w carbon resister	Protection from motor kickback
R-10	D	2.2KEBK-NT	2.2k @ 1/8 carbon film register1	Current limit, power transistor
R-11	D	22KEBK-NT	22k @ 1/8 carbon film resister	Reverse lock adjustment trim
R-12	D	47KEBK-NT	47k @ 1/8 carbon film resister	Feedback, direction flip-flop
R-13	D	47KEBK-NT	47k @ 1/8 carbon film resister	Current limit, cutoff
R-14	D	10MEBK-NT	10M @ 1/8 carbon film resister	Feedback, U2-A
R-15	D	15KEBK-NT	15k @ 1/8w carbon film resisters	Reverse lock adjustment trim
R-16,17	D	15KEBK-NT	15k @ 1/8w carbon film resisters	Current Limit, Direction op-amp
R-18,19	D	15KEBK-NT	15k @ 1/8w carbon film resisters	Current Limit, direction relay
R-20,21	D	100KEBK-NT	100K @ 1/8w carbon film resister	Voltage divider, U1-A
R-22,23	D	100KEBK-NT	100K @ 1/8w carbon film resister	Voltage divider, U1-B
R-24	D	100KEBK-NT	100K @ 1/8w carbon film resister	Bias, Reversing U1-B
R-25,26,27 ,28,29,30,31	D	100KEBK-NT	100K @ 1/8w carbon film resister	Bias, direction U1-C and U1-D
R-32,33	D	100KEBK-NT	100K @ 1/8w carbon film resister	Pulse Generator
R-34,35	D	100KEBK-NT	100K @ 1/8w carbon film resister	Voltage Divider, Cutoff
R36	D	100KEBK-NT	100K @ 1/8w carbon film resister	Frequency Adjust trim
R-37,38	D	100KEBK-NT	100K @ 1/8w carbon film resister	Voltage Divider, U2-C
R-39	D	100KEBK-NT	100K @ 1/8w carbon film resister	Pulse Strength current limiter
R-40	D	100KEBK-NT	100K @ 1/8w carbon film resister	Speed current from U2-D
R-41,42	D	100KEBK-NT	100K @ 1/8w carbon film resister	Voltage Divider, U2-D
R-43	D	100KEBK-NT	100K @ 1/8w carbon film resister	Pulse strength trim

Miscellaneous

D	V1044-ND	Vector 8001 circboard pattern “D”	Project board
D	V1055-ND	Vector K24 Test pins	Optional or as required
D	A94120-ND	20-pin IC socket	IC-1
D	929974-01-36-ND	Sip female Header*	connect buttons to board
D	929834-02-36-ND	Sip male Header*	Jumpers, connections
D	S9003	Jumpers	Device addressing
D	S1122-36-ND	Right angle header*	Battery connection to charger
D	HS135-ND	Heat sink*	Power Amplifier Transistor
D	PC51-ND	Blank Copper Clad PC Board *	Transmit & receive modules
D	Various	Assorted #6 screws*, nuts and washers

* modified

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FURTHER INFORMATION

Most vendors supply both pictures, specifications sheets that contain pinouts and electrical information on how to use a given part as shown in the following sample PDF files:

CIPP-encoder/decoder chips

Linx long range Receiver

Linx long range transmitter

Reynolds RF Transmitter and Receiver

Back to Table of Contents

		The Linx Technologies family of modules includes matching radio frequency transmitters and receivers that are perfectly suitable for model railroad use along with antennas, evaluation kits and a number of support products. These 3-volt hybrid modules are extremely rugged, easy to use, an excellent value for the price and designed specifically for battery power.
These modules use surface mounting technology for direct soldering to a PC board about the size of a TV remote control. Linx specifications state that there should be a backplane surface or layer of copper cladding behind this circuit for optimum operation. Reynolds Electronics uses Linx products in many of its products and sells these modules already mounted on a backplane along with several additional products used in these throttle circuits.
The only other component required to make a complete transmitter is the antenna. Be sure to read the Linx specifications for the layout of the ground plane, Transmitter Module, and antenna. A plain #22 wire cut to the right length works quite well in a normally sized train room but it is a bit crude. Here are three other forms antennas that are common and easily used.
The traditional monopole external antenna will yield the maximum range of up to 3000 feet outside and about half that indoors.	This antenna mounts directly on the PC board like any other component and gives performance similar to a monopole. It is a bit more directions however you will never know it in a train room					Wound Coil antennas do not quite have as much range as others but are very inexpensive and work extremely well in a train room. Hint: do NOT bend or distort the coil in any way.
This receiver daughter board shows the relationship of the antenna to the receiver module. This board started as a blank double-clad PC board. The backside is blank behind the antenna and completely solid behind the receiver. Use a knife to cut the groves in the copper cladding to form the pads and traces as required and peel away the excess cladding. Widen these groves a triangular file as required. This process may be a bit slow and tedious compared to etching the design but is faster when only two or three parts are required and avoids using hazardous chemicals and everything that goes with them.
				Linx Technologies offers these self-contained evaluation boards to demonstrate how easy it is to interface additional components the transmitter and receiver modules. Back to Index

Propulsion Power Wave Forms The most vexing problem in model railroad operation is the transition of a locomotive from a standing to a slow speed start. A locomotive, all too often, will remain static as the throttle advances to a certain point and then suddenly jump to life. Flywheels can help but there is not always room for one, especially in small locomotives. Steam engines are especially prone to this situation because of the added friction of the running gear and side-rod motion. The following explains several electrical solutions designed to overcome this problem.
The diagram to the right shows the performance of a typical locomotive running on pure Direct Current (DC). Note how the speed remains zero until it suddenly jumps to running speed. This is true for all DC motors to one extent or other due to the unequal magnetic forces exerted on the stators as each passes the stationary permanent magnets of the motor. A slight increase of voltage also causes a speed-up of the motor. Once the motor is running, the speed becomes closer in proportion to the track voltage applied. Modern motors have skewed stators and better magnets that surround the motor to reduce, but not eliminate, this effect.
				Using the unfiltered alternating current (AC) of a Transformer converted to DC is better than pure DC as the uneven pulses of current tend to help the motor start turning. The use of a full wave rectifier offers an improvement over pure DC that is slight but noticeable. The only penalty is that the motor may run slightly warmer than pure DC
This circuit shows the result of using a half wave rectifier. The spaces between the wave peaks give a stronger “kick” to get the motor started. This yields much smoother operations at slow speeds and in addition helps by burnishing the rails and removing dirt from between the railhead and wheels of a locomotive. All this however is at the penalty of generating noticeably more heat in the motor and a great deal of wear between the gears and drive train within a locomotive not. Running an engine at normal speeds with this type of power also causes excessive heat and can damage the motor’s magnets.
Early Transistor throttles were a throwback to pure DC, operationally speaking and motors again had the same problem of overcoming slow starts. Then, as time passed, small amounts of AC ripple injected into the DC again brought back improved starts. Transistor throttles however can cause several problems when a locomotive hits a bit of dirt on the tracks. The first problem with transistors in throttle circuits occurs when they act to vary current to maintain a given voltage. Rapid fluctuations in voltages occur as dirt causes the contact between the rail and wheels is lost or regained. The transistor in turn causes great changes in current that is strong enough to sometimes burn small pits in the railhead. Second, this same lost of contact works in reverse from the motor. A motor can be a generator such that when the wheels again contact the railhead, high voltage spikes generated by the motor can damage the transistor. Another problem can be the heat a transistor generates. A transistor generates the most heat when “half on” or about a track voltage of six volts. The realism of the throttle and braking action involved overcome these drawbacks.
	Silicon Controlled Rectifier (SCR) circuits add new factors into the equation of an ultimate throttle. This waveform is either 0v or 12v with the widths of each wave varying from extremely narrow for a stationary engine to almost full width for top speed. This is ideal as far as the electronics are concerned because the SCRs generate very little heat, thus almost no heat sinks are required. A DCC system decoder presents this waveform to the engine’s motor.
Unfortunately, there are several drawbacks. The inductive load of a motor coupled to the rapidly changing voltages at the edges of each square wave produce high spikes of voltage and current, especially on dirty track. These spikes are quite damaging to the permanent magnet of any DC motor. A good motor can last thirty years or more before the magnets wear out however this waveform destroys them in less than three. This waveform also causes pitting of the railhead especially on dirty track thus aggravating an already problematic situation.								A complete SCR throttle
			This chart represents the complex waveforms of a generic DCC system. The actual voltage across the rails is a modified, 12-volt waveform with only (2) possible widths allowed and representing four bytes of digital information. Two of these bytes select a device while the other two determine to what extent The decoder of an engine translates speed information and using a series of pre-programmed tables, it then outputs a voltage such that the locomotive smoothly increases its speed at a constant rate as the throttle is advanced. Note that within the first jump of speed the strength and frequency of an additional waveform modifies the waveform to improve the DC component of the motor voltage to provide a smooth start.
There is one further point to consider about the speed table of a DCC throttle. The purpose of the table is to have the motor increase in speed in direct proportion to a potentiometer used to control speed. Some throttles use simple pushbuttons and resisters to control the speed. On this type of throttle, the effect of the speed table is irrelevant as the engineer simply pushes a button to increase of decrease a locomotive to the desired speed.
		This throttle presents a varying amount of voltage to the tracks as in a common throttle but it has a special circuit to start an engine. This replaces the complex programming of the receiver and the associated equipment and learning curve of DCC. Control settings for the frequency, duty cycle, strength and the point at which it fades to pure DC all vary the waveform imposed on the pure DC control voltage. All waveforms are AC avoiding the problems inherent with a square wave circuit. The push-button control and a personality module eliminate the need for any speed tables.
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Bob Van Cleef, MMR

Last update
11/23/2008