ELECTROCARDIOGRAM HEART MONITOR KIT Ramsey Electronics Model No. ECG1 An educational kit to apply the principles of differential amplifiers while monitoring your heart rhythm! Actually monitors your heart rhythm and displays it with a flashing light! A must for the budding intern, with ultra safe low voltage operation.
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Ramsey Publication No. MECG1 Price $5.00 KIT ASSEMBLY AND INSTRUCTION MANUAL FOR ELECTOCARDIOGRAM HEART MONITOR KIT TABLE OF CONTENTS Introduction ................................. 4 Circuit Description....................... 7 Schematic Diagram .................... 9 Parts Layout Diagram ................. 10 Parts List .................................... 11 Assembly Instructions ................. 13 Using your ECG1 ........................ 20 Troubleshooting Guide ............... 21 Warranty ...........
IMPORTANT NOTE: This Ramsey Electronics kit is NOT intended for any medical usage. It is simply for experimenters and hobbyists who wish to observe an EKG waveform using common components and commercially available sensors. Every reasonable precaution was used in the design and manufacture of this product to make it an accurate monitor, but you cannot draw any conclusions from the results (you may, however, astound your physician with your knowledge of EKG operation).
This filling and pushing action is accomplished using specialized one way valves. There are four of these valves, one for each chamber. These valves allow the blood to exit when the chamber contracts, then close to allow the chamber to fill with fresh blood for the next beat. The right side of the heart is devoted to pumping the oxygen depleted blood to the lungs. After the lungs have oxygenated the blood it is returned to the left side of the heart where it is pumped throughout the body.
right ventricles. The impulse continues through the Purkinje fibers causing the ventricles to contract and squeezing the blood on its way throughout the body. In the time that this is happening, the atria are resetting for the next beat, or repolarizing. The polarization effect on the muscle cells is due to ionicmolecular level function of the individual cells, and the ionic compounds (including sodium (Na), potassium (K), and calcium (Ca)) contained in the cells themselves.
When we measure the impulses electrically, the pattern will appear similar to this: QRS T P Atrial Ventricular Depolarization Depolarization Ventricular Repolarization Hopefully now the ECG patterns seem a little less “mystical ” than they were when we began, and we have cleared up how the pulses are created and how they correspond to the action of the heart muscle.
call the differential change a normal mode. A well designed differential amplifier has a large common mode rejection level (CMRR), or the ratio of response for the normal mode to the response of the common mode signal of the same level. The differential circuit is used extensively in modern electronics circuits. There is a great amount of common noise present on most long runs of wire (telephone transmission, theater audio, computer networking, etc.
ECG1 SCHEMATIC DIAGRAM ECG1 • 9
ECG1 PARTS PLACEMENT DIAGRAM ECG1 • 10
PARTS SUPPLIED WITH YOUR ECG1 KIT Capacitors 7 .1 µF disc capacitor (marked .1 or 104 or 100 nF) [C1,2,6,7,8,9,18] 1 470 pF disc capacitor (marked 470 or 471) [C5] 1 1 µF electrolytic capacitors [C4] 7 10 µF electrolytic capacitors [C3,10,12,13,14,16,17] 3 100 µF electrolytic capacitors [C11,15,19] Resistors and Potentiometers 1 2 ohm (red-black-gold) [R16] 1 470 ohm (yellow-violet-brown) [R17] 1 4.
RAMSEY "Learn-As-You-Build KIT ASSEMBLY There are numerous solder connections on the ECG1 printed circuit board. Therefore, PLEASE take us seriously when we say that good soldering is essential to the proper operation of your EKG kit! • • • Use a 25-watt soldering pencil with a clean, sharp tip. Use only rosin-core solder intended for electronics use. Use bright lighting; a magnifying lamp or bench-style magnifier may be helpful. Do your work in stages, taking breaks to check your work.
ECG1 ELECTROCARDIOGRAM KIT ASSEMBLY Although we know that you are anxious to complete the assembly of your electrocardiogram kit it is best to follow the step-by-step instructions in this manual. Try to avoid the urge to jump ahead installing components. Since you may appreciate some warm-up soldering practice as well as a chance to put some landmarks on the PC board, we’ll first install some of the larger mounting components.
2. Identify J3, the 3.5mm mono jack. Again, slide this through the circuit board and solder all three leads securely. This jack will act a monitor output port for your kit, providing a convenient hookup for an oscilloscope to give a visual display of an EKG waveform. 3. Install J1, the last stereo type jack. Careful with those leads; make sure that they all make it through the board before you solder them into place. J1 acts as the connection point for the probes to the circuit inputs. 4.
8. Install R16, 2 ohms (red-black-gold). 9. Install C18, .1 µF disc capacitor (marked 104 or .1). Disc capacitors are not polarized; they can be installed in either direction. The reason we call them “disc” caps can be seen in the package. The capacitor itself is two conductive discs separated by a dielectric compound.
18. Install C8, .1 µF disc capacitor (marked 104 or .1). 19. Install R9, 100k ohms (brown-black-yellow). 20. Install R12 and R10, both 100k ohms (brown-black yellow). 21. Identify C11, 100 uF electrolytic capacitor (small cylindrical component coated with plastic and marked 100uF). Electrolytic capacitors are polarized with a (+) and (-) lead and must be installed in the correct orientation. Use care to ensure proper polarity. See the parts diagram for proper placement.
operation. Mount it as close to the board as possible without forcing it. Carefully solder all three leads 34. Using a scrap component lead, form a jumper wire and install in the JMP2 holes. 35. Install R17, 470 ohms (yellow-violet-brown). Next we will install the LED beat indicator for the display. (L)ight (E)mitting (D) iodes are just that, a diode junction that emits light of a particular wavelength when forward biased.
couple of pointers. Remember to install the connector cover when requested; it can save time and the aggravation of unsoldering and resoldering the connectors. When soldering to the connectors themselves use enough time and solder to create a robust connection but don’t leave your iron on the connection for an excessive amount of time as it can melt the plastic insulator on the connector itself. It is helpful to hold the connector in place with a small vise to aid in soldering. 42.
CONGRATULATIONS ! Your ECG monitor is now complete! Have a final look over your work, paying particular attention to the orientation of diodes, capacitors, and IC’s. Remember that any problems you find now can save time and effort after the unit has been cased up. ASSEMBLY INSTRUCTIONS FOR CUSTOM CASE The enclosure is a key element to the overall pride you will have upon completing your Ramsey kit. The enclosure will show how you were able to “build from scratch” a commercial piece of high-tech electronics.
USING YOUR ECG1 ELECTROCARDIOGRAM Now we’re ready for the moment of truth, the initial power up and running of your ECG1. Be ready to energize the unit by installing a fresh 9 volt battery in place and connected to the snap tab. You may want to install a set of headphones or small speaker to the audio out jack as well. Start with both the volume and gain set to the lowest (rotate CCW) positions.
monitor. Feel free to experiment with other electrode positions. One of the favorites around the lab here is the “valley” method. The ground probe is placed on the stomach or wrist and the differential probes placed at the base of the sternum and the other just below the neck line. The newlyweds have also come up with a method of placing a differential probe on each chest while the ground is placed on one wrist, and listening for the two sets of ECG waveforms.
While we had hoped that it wouldn’t come to this, if you are still having trouble with your ECG, here are a few additional suggestions. Use a methodical, logical troubleshooting technique. Most problems can be solved using common sense. A volt-ohm meter and a clear head are usually all that are needed to correct any problem. Most problems are due to misplaced parts and/or bad solder connections. Working backwards through the assembly steps will often lead you to the problem.
The Ramsey Kit Warranty Please read carefully BEFORE calling or writing in about your kit. Most problems can be solved without contacting the factory. Notice that this is not a "fine print" warranty. We want you to understand your rights and ours too! All Ramsey kits will work if assembled properly. The very fact that your kit includes this new manual is your assurance that a team of knowledgeable people have field-tested several "copies" of this kit straight from the Ramsey Inventory.
ECG1 ELECTROCARDIOGRAM KIT Quick Reference Page Guide Introduction ...................................... 4 Circuit description ............................ 7 Schematic diagram .......................... 9 Parts layout Diagram ....................... 10 Parts list ........................................... 11 Assembly instructions ...................... 13 Using your ECG1 ............................. 20 Troubleshooting guide ..................... 21 Warranty ..........................................
