1. Lecture 10: Disposable Camera
Coil
Flash
Battery
Charging Switch
Trigger
Lecture 10: Disposable Camera
Learning Engineering Using Inexpensive Products That May Be Found Around The House
Or Apartment or Dorm Room
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

2. Introduction to Engineering Electronics
Electrical Safety
Note on the diagram of the camera that voltages as high as 320V exist in this circuit
It is current, not voltage, that heats a wire and that causes damage to humans.
The salty fluids of the human body are electrical conductors.
The interior resistance of an arm, from hand to shoulder is about 100 Ohms.
Introduction to Engineering Electronics
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9/17/2018

3. Introduction to Engineering Electronics
Electrical Safety
Any voltage across the internal resistance will cause currents to flow and heat to be generated sufficient to cause damage to tissue.
Much more significantly, the nervous system and its means of control over muscles (including the heart) are electrochemical. Thus, damage can occur at currents much less than those necessary to cause burns.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

4. Electrical Safety: Current Physiological Reaction (60 Hz)
< 1mA
None
1mA
Perception Threshold
1-3 mA
Mild Sensation
3-10 mA
Painful Sensation
10 mA
Paralysis Threshold of Arms
30 mA
Respiratory Paralysis
75 mA
Fibrillation Threshold (0.5%)
250 mA
Fibrillation Threshold (99.5%)
4 A
Heart Paralysis Threshold
>5 A
Burning
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

5. Introduction to Engineering Electronics
Electrical Safety
One of the key characteristics that distinguishes an EE, CSE or EPE from other technical professionals is an understanding of electrical safety.
It is particularly important to be able to estimate currents from known voltages, since voltages are easier to measure and generally more controllable.
Thus, if you learn nothing else from IEE, you should learn that:
Ohm’s Law can save your life and the lives of others.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

6. Electrical Safety: How To Avoid Shock
Estimate voltages and currents and act cautiously.
Resistance of dry skin offers protection below 50 V. Typically, skin inserts 10k to 100k Ohms of resistance between an outside conductor and internal fluids.
Skin provides safe current limiting below 50 V if it is dry.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

7. Electrical Safety: How To Avoid Shock
When working with voltages above 100 V, exercise great care.
If you must work with these voltages, a famous rule is to keep one hand in your pocket because arm-to-arm current through your heart is much worse neurologically than local currents through one limb.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

8. Electrical Safety: References
Remember the one hand rule
MIT Lab Safety
NASA Lab Safety
Tecra Tools Electrical Safety
University of Tennessee Power Electronics Lab Safety
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

9. Introduction to Engineering Electronics
Electrical Safety
It is possible to come in contact with high voltages with little permanent harm as long as currents are small.
Stun guns work at voltages typically between 20kV and 150kV and usually do not cause permanent damage since currents are small (a few microamps) and voltages are pulsed (1 microsecond).
We will return to the topic of stun guns at the end of this lecture.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

10. 2 Minute Quiz Name______Sec______Date______
True or false – proper electrical safety procedures require that we always know at least approximately what currents we will encounter in a circuit.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

11. Disposable Camera Electronics
This is the circuit you will be building in the lab using a disposable camera.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

12. Disposable Camera Electronics
Coil
Flash
Battery
Charging Switch
Trigger
This is the circuit mentioned in lecture 6 which can be used to launch a piece of a paper clip up to 50 feet.
The coil is soldered in series with the flash tube.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

13. Disposable Camera Electronics
There are many different types of disposable cameras. All open differently.
Once you remove the film for processing (this can be done by the developer), you can use the remaining circuit and battery.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

14. Disposable Camera Electronics
Capacitor
Note that the capacitor can still be charged, even if the camera has not been used for a while. Many cameras automatically charge between shots.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

15. Disposable Camera Electronics
Flash Tube
Capacitor
Transformer
The circuit board, once removed, is quite simple.
Shown above are both the top and bottom views of the circuit board.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

16. Disposable Camera Electronics
The cover can be pried off.
Once you remove the cover, observe how the mechanical apparatus works (gears, shutter, lens, springs, etc).
You may find these useful in applications.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

17. Disposable Camera Electronics
The Exploratorium recommends that you use rubber gloves to avoid shock.
Pry off the case using a screwdriver
You should be able to set the shutter mechanism using intact gears, etc.
You can recharge the capacitor using the charge button (or short across the pads).
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

18. Disposable Camera Electronics
While charging, you should hear a high pitched whine. This is the oscillator circuit.
Fire the circuit by triggering the shutter – the flash should go off.
Introduction to Engineering Electronics
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9/17/2018

19. Disposable Camera Electronics
The oscillator produces a time varying voltage (sort of sinusoidal) from the 1.5V battery.
A time varying voltage is necessary to produce a high voltage using a transformer.
The high voltage output from the transformer is rectified using diodes to produce a high DC voltage to charge a capacitor.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

20. Disposable Camera Electronics
Once the high voltage (320V) capacitor is charged, a small neon bulb will light up.
The charging is then stopped either manually (you stop pushing on the charge switch) or automatically.
Then when the shutter is engaged, a switch is closed which triggers the flash lamp.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

21. Disposable Camera Electronics
The flash lamp has three electrodes:
Two connected across the high voltage capacitor
One connected to a pulse transformer
The third electrode provides a short very high voltage pulse to ionize the xenon gas in the flash tube. Once the gas is ionized, it will carry current and discharge the capacitor. The current from the capacitor provides the energy for the high intensity light.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

22. Disposable Camera Electronics
This is the circuit diagram for the camera used in the lab.
Introduction to Engineering Electronics
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9/17/2018

23. Disposable Camera Electronics
A transformer is used to step up or step down voltages and currents.
Introduction to Engineering Electronics
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9/17/2018

24. Disposable Camera Electronics
The secondary voltage V2 is equal to N times the primary voltage V1.
Introduction to Engineering Electronics
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25. Disposable Camera Electronics
The turns ratio N is equal to the ratio of the number of secondary windings to the number of primary windings. For a step up transformer this ratio is greater than 1.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

26. Disposable Camera Electronics
You will also connect a trigger circuit in the lab to make the camera flash when light levels change. To operate the circuit, you need 5V which is obtained from the battery using a DC-DC converter.
Introduction to Engineering Electronics
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9/17/2018

27. Disposable Camera Electronics
The lab circuit again
Introduction to Engineering Electronics
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9/17/2018

28. Disposable Camera Electronics
Note that the wires from the protoboard circuit must be soldered to the camera circuit.
Introduction to Engineering Electronics
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9/17/2018

29. 2 Minute Quiz Name______Sec______Date______
In the disposable camera circuit, estimate the number of turns on the transformer?
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

30. Disposable Camera Electronics: References
Disposable Camera Electronics from the Exploratorium
Disposable Camera Dissection from the Exploratorium
Disposable Camera Lab from the University of Washington
Dissecting Disposable Cameras for Parts
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

31. Introduction to Engineering Electronics
Soldering
Your TA will show you how to solder.
Place parts mechanically first, if possible.
Apply enough heat.
Watch for cold solder joints.
How to Solder
How to Solder Like a Pro
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

32. Introduction to Engineering Electronics
Cold Solder Joints
Note that cold solder joints tend to form ball shapes and do not make contact between wires and pc boards
Properly heated solder should flow
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

33. Introduction to Engineering Electronics
Stun Guns
Outer electrodes must come in contact with attacker.
Inner electrodes are closer together and thus can spark at the high voltages used to deter attackers.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

34. Stun Guns: What is Inside?
This is what is inside a cheap stun gun (provided by someone who likes to take things apart).
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

35. Stun Guns: What is Inside?
Oscillator voltage is stepped up to a fairly high voltage with a transformer.
This is used to charge a capacitor through a rectifier made with four diodes.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

36. Stun Guns: What is Inside?
When the voltage across the capacitor is high enough to spark across the gap, a short pulse is created across the primary of a pulse transformer and a large voltage pulse results.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

37. Stun Guns: What is Inside?
The spark gap is simply the two pieces of metal strip in a cross shape. A much larger spark gap was used in the can crusher discussed in lecture 7.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

38. Stun Guns: What is Inside?
The first transformer is shown at the left.
The pulse transformer is shown at the right. Note that it is potted so that it can operate at higher voltages.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

39. Introduction to Engineering Electronics
Tesla Coil
Nikola Tesla – The father of AC and a certifiable mad scientist, is one of the most interesting electrical scientist/engineers who has ever lived.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

40. Introduction to Engineering Electronics
Tesla Coil
On this and the last slide is shown a small lab scale Tesla Coil
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

41. Introduction to Engineering Electronics
Tesla Coil
The circuit has some similarities to the flash tube and stun gun. Note the two transformers and the spark gap. The resonance effect (L and C) also plays a large role in making the voltage large enough to cause sparks.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

42. Introduction to Engineering Electronics
Tesla Coil
This is Tesla’s Wardenclyffe Lab in Shorham Long Island where he planned to use this huge coil to transmit radio across the planet.
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

43. Introduction to Engineering Electronics
2 Minute Quiz ANSWERS
True or false – proper electrical safety procedures require that we always know at least approximately what currents we will encounter in a circuit. TRUE
# turns = Vo/Vin=320/1.5=213
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018

44. Where Will You See This Material Again?
Circuits, Electronics, Components
ECSE-2010 Electric Circuits
ECSE-2050 Analog Electronics
ECSE-2060 Digital Electronics
Transformers
ECSE-2100 Fields and Waves I
Applications of Electronics
Many classes
Introduction to Engineering Electronics
STOLEN FROM K. A. Connor
9/17/2018