SINGLE CHIP FM RADIO

Single Chip FM Radio Circuit

This to a great degree basic FM radio recipient circuit is made conceivable by the extraordinary reason TDA7000 IC. It coordinates about every one of the capacities important to construct a FM recipient requiring just a couple of outside capacitors and a tuning circuit. Utilizing a basic dynamic RC channel made of just a solitary inductor, a couple of resistors and a varicap, this FM recipient will get show radio between around 88 and 108 MHz. The mono yield sign can then be utilized to drive an arrangement of high impedance earphones, or food a force speaker.

Part	Total Qty.	Description	Substitutions
C1, C9, C12, C17	4	0.1uF Ceramic Disc Capacitor
C2, C4, C5, C6, C13	5	0.01uF Ceramic Disc Capacitor
C3	1	20pF Ceramic Disc Capacitor	See Notes
C7, C15, C16	3	0.001uF Ceramic Disc Capacitor
C8, C10, C11	3	220pF Ceramic Disc Capacitor
C14	1	100pF Ceramic Disc Capacitor
C18	1	200pF Ceramic Disc Capacitor
R1	1	22K 1/4W 5% Resistor
R2	1	100K 1/4W 5% Resistor
R3	1	100K Linear Taper Pot
D1	1	Motorola MV209 Varicap VHF Tuning Diode
U1	1	TDA7000 FM Radio IC	See Notes
L1	1	7 Turn Inductor (See Notes)
MISC	1	Board, Wire, Socket For U1, Case

Tragically, the TDA7000 went old a couple of years prior. The first form is made by Signetics (now Philips) and is getting a touch hard to discover nowadays. There are, then again, different choices. Philips makes the TDA7010T which is a surface mount form. The TDA7021T is likewise accessible which incorporates stereo capacity. They are electrically comparative however are just 16 pin chips so you'll have to contrast the datasheets with manufacture the circuit. 

The estimation of C3 is noncritical and can be somewhere around 10pF and 20pF. Minor changes in accordance with L1 may be obliged taking into account the estimation of C3. 

L1 is made by winding 7 turns of 24 AWG wire around pencil. Uproot the pencil and after that space the turns marginally. 

Recurrence choice is by means of R3.

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AIRCRAFT RADIO COMMUNICATION RECEIVER

Aircraft Radio Communications Receiver

The correspondences between business flying machine and the ground can be intriguing, interesting and once in a while notwithstanding exasperating. However radios that get the give or take 220MHz to 400MHz band regularly utilized for airplane (both military and business) are not effectively found. What's more, scanners can be entangled, extensive and extravagant. With a simple to fabricate circuit, for example, this one, everybody can appreciate listening in on these discussions.

Part Total Qty. Description Substitutions R1, R3 2 47K 1/4W Resistor R2 1 10K 1/4W Resistor R4 1 4.7K 1/4W Resistor R5 1 5K Linear Taper Pot R6 1 2.2K 1/4W Resistor C1, C2, C3, C6 4 0.001uF Ceramic Disc Capacitor C4 1 2.2pF Ceramic Disc Capacitor C5 1 1pF Ceramic Disc Capacitor C7 1 15uF 15V Electrolytic Capacitor C8 1 18pF Variable Capacitor D1 1 1N82 Diode Q1 1 2N918 NPN Transistor L1 1 See Notes L2 1 1.8uH Inductor ANT1 1 Approx. 18 Inch Wire Antenna MISC 1 PC Board, Wire, Knob For C8

NOTE ;

The circuit initially showed up in the Think Tank section of the Sept. 1995 issue of Popular Electronics. 

L1 is made by winding 2 turns of 22 AWG magnet wire on a 5/32 bore. This inductor can be adjusted to move the recurrence scope of the circuit. 

The radio wire can likewise be set at the anode of D1 if over-burden is an issue with it joined with the emitter of Q1 

R5 modifies regen and along these lines affectability.

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DIGITAL VOLUME CONTROL

Digital Volume Control

This is the simple circuit 

Part	Total Qty.	Description	Substitutions
C1	1	0.1uf Ceramic Disc Capacitor
U1	1	DS1669 Digital Pot IC (See Notes)
S1, S2	2	Momentary Push Button Switch
MISC	1	Board, Wire, Socket For U1

NOTE :

1. S1  volume up, S2 volume down.


2. The input signal should not less than  -0.2 volts.


3. Using a dual polariity power supply (+-5V works fine) will cure most clipping problems. You will have to check the data sheet for the correct pins to connect your voltages.

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FM TRANSMITTER

FM Transmitter

Here is the schematic, PC board example, and parts position for a low controlled FM transmitter. The scope of the transmitter when running at 9V speaks the truth 300 feet. Running it from 12V expands the reach to around 400 feet. This transmitter ought not be utilized as a room or phone bug.

Schematic

Part	Total Qty.	Description	Substitutions
C1	1	0.001uf Disc Capacitor
C2	1	5.6pf Disc Capacitor
C3,C4	2	10uf Electrolytic Capacitor
C5	1	3-18pf Adjustable Cap
R1	1	270 Ohm 1/8W Resistor	270 Ohm 1/4W Resistor
R2,R5,R6	3	4.7k 1/8W Resistor	4.7K 1/4W Resistor
R3	1	10k 1/8W Resistor	10K 1/4W Resistor
R4	1	100k 1/8W Resistor	100K 1/4W Resistor
Q1, Q2	2	2N2222A NPN Transistor	2N3904, NTE123A
L1, L2	2	5 Turn Air Core Coil
MIC	1	Electret Microphone
MISC	1	9V Battery Snap, PC Board, Wire For Antenna

NOTE:

L1 and L2 are 5 turns of 28 AWG lacquer covered magnet wire twisted with an inside distance across of around 4mm. Within a ballpoint pen functions admirably (the plastic tube that holds the ink). Uproot the structure in the wake of twisting then introduce the loop on the circuit board, being mindful so as not to curve it. 

C5 is utilized for tuning. This transmitter works on the typical telecast frequencies (88-108MHz). 

Q1 and Q2 can likewise be 2N3904 or something comparable. 

You can utilize 1/4 W resistors mounted vertically rather than 1/8 W resistors. 

You may need to sidestep the battery with a .01uf capacitor. 

A radio wire may not be needed for operation.

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3 WATT FM TRANSMITTER

3 Watt FM Transmitter

This is the schematic for a FM transmitter with 3 to 3.5 W yield control that can be utilized somewhere around 90 and 110 MHz. In spite of the fact that the steadiness isn't so terrible, a PLL can be utilized on this circuit. 

This is a circuit that I've construct a couple of years prior for a companion, who utilized it as a part of mix with the BLY88 speaker to acquire 20 W yield power. From the notes that I made at the first schematic, it worked fine with a SWR of 1 : 1.05 (truly ordinary at my place with my radio wire).

Part	Total Qty.	Description	Substitutions
R1,R4,R14,R15	4	10K 1/4W Resistor
R2,R3	2	22K 1/4W Resistor
R5,R13	2	3.9K 1/4W Resistor
R6,R11	2	680 Ohm 1/4W Resistor
R7	1	150 Ohm 1/4W Resistor
R8,R12	2	100 Ohm 1/4W Resistor
R9	1	68 Ohm 1/4W Resistor
R10	1	6.8K 1/4W Resistor
C1	1	4.7pF Ceramic Disc Capacitor
C2,C3,C4,C5,C7,C11,C12	7	100nF Ceramic Disc Capacitor
C6,C9,C10	3	10nF Ceramic Disc Capacitor
C8,C14	2	60pF Trimmer Capacitor
C13	1	82pF Ceramic Disc Capacitor
C15	1	27pF Ceramic Disc Capacitor
C16	1	22pF Ceramic Disc Capacitor
C17	1	10uF 25V Electrolytic Capacitor
C18	1	33pF Ceramic Disc Capacitor
C19	1	18pF Ceramic Disc Capacitor
C20	1	12pF Ceramic Disc Capacitor
C21,C22,C23,C24	4	40pF Trimmer Capacitor
C25	1	5pF Ceramic Disc Capacitor
L1	1	5 WDG, Dia 6 mm, 1 mm CuAg, Space 1 mm
L2,L3,L5,L7,L9	5	6-hole Ferroxcube Wide band HF Choke (5 WDG)
L4,L6,L8	3	1.5 WDG, Dia 6 mm, 1 mm CuAg, Space 1 mm
L10	1	8 WDG, Dia 5 mm, 1 mm CuAg, Space 1 mm
D1	1	BB405	BB102 or equal (most varicaps with C = 2-20 pF [approx.] will do)
Q1	1	2N3866
Q2,Q4	2	2N2219A
Q3	1	BF115
Q5	1	2N3553
U1	1	7810 Regulator
MIC	1	Electret Microphone
MISC	1	PC Board, Wire For Antenna, Heatsinks

NOTE :

The circuit has been tried on an ordinary RF-testing breadboard (with one side copper). Make a few associations between the two sides. Fabricate the transmitter in a RF-confirmation packaging, utilize great connectors and link, make a protecting between the diverse stages, and be mindful of the various RF tenets of building. 

Q1 and Q5 ought to be cooled with a warmth sink. The case-pin of Q4 ought to be grounded. 

C24 is for the recurrence modification. Alternate trimmers must be changed in accordance with greatest yield power with least SWR and information current. 

Nearby laws in a few states, territories or nations may disallow the operation of this transmitter. Check with the neighborhood powers.

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CAR BATTERY CHAGER

Car Battery Charger

This charger will rapidly and effectively charge most any lead corrosive battery. The charger conveys full current until the current drawn by the battery tumbles to 150 Mama. As of now, a lower voltage is connected to complete off and keep from over charging. At the point when the battery is completely charged, the circuit switches off and lights a Drove, letting you know that the cycle has wrapped up.

Part	Total Qty.	Description	Substitutions
R1	1	500 Ohm 1/4 W Resistor
R2	1	3K 1/4 W Resistor
R3	1	1K 1/4 W Resistor
R4	1	15 Ohm 1/4 W Resistor
R5	1	230 Ohm 1/4 W Resistor
R6	1	15K 1/4 W Resistor
R7	1	0.2 Ohm 10 W Resistor
C1	1	0.1uF 25V Ceramic Capacitor
C2	1	1uF 25V Electrolytic Capacitor
C3	1	1000pF 25V Ceramic Capacitor
D1	1	1N457 Diode
Q1	1	2N2905 PNP Transistor
U1	1	LM350 Regulator
U2	1	LM301A Op Amp
S1	1	Normally Open Push Button Switch
MISC	1	Wire, Board, Heatsink For U1, Case, Binding Posts or Alligator Clips For Output

NOTE :

The circuit was intended to be powered by a power supply, which is the reason there is no transformer, rectifier, or channel capacitors on the schematic. There is no motivation behind why you can't include these. 

A heatsink will be required for U1. 

To utilize the circuit, connect it to a power supply/connect it to. At that point, join the battery to be charged to the yield terminals. All you need to do now is push S1 (the "Begin" switch), and sit tight for the circuit to wrap up. 

On the off chance that you need to utilize the charger without needing to give an outside power supply, utilize the accompanying circuit.

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6V TO 12V CONVERTER

6V to 12V Converter

This inverter circuit can provide up to 800mA of 12V power from a 6V supply. For example, you could run 12V car accessories in a 6V (British?) car. The circuit is simple, about 75% efficient and quite useful. By changing just a few components, you can also modify it for different voltages.

Part	Total Qty.	Description	Substitutions
R1, R4	2	2.2K 1/4W Resistor
R2, R3	2	4.7K 1/4W Resistor
R5	1	1K 1/4W Resistor
R6	1	1.5K 1/4W Resistor
R7	1	33K 1/4W Resistor
R8	1	10K 1/4W Resistor
C1,C2	2	0.1uF Ceramic Disc Capacitor
C3	1	470uF 25V Electrolytic Capcitor
D1	1	1N914 Diode
D2	1	1N4004 Diode
D3	1	12V 400mW Zener Diode
Q1, Q2, Q4	3	BC547 NPN Transistor
Q3	1	BD679 NPN Transistor
L1	1	See Notes
MISC	1	Heatsink For Q3, Binding Posts (For Input/Output), Wire, Board

NOTE:

• L1 is a custom inductor wound with about 80 turns of 0.5mm magnet wire around a toroidal core with a 40mm outside diameter.
• Different values of D3 can be used to get different output voltages from about 0.6V to around 30V. Note that at higher voltages the circuit might not perform as well and may not produce as much current. You may also need to use a larger C3 for higher voltages and/or higher currents.
• You can use a larger value for C3 to provide better filtering.
• The circuit will require about 2A from the 6V supply to provide the full 800mA at 12V.

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12V SOLAR INVERTER BATTERY CHARGER

12V Solar Inverter Battery Charger

Here is a vitality sparing sun oriented inverter battery charger. It gathers sunlight based vitality to recharge 12 volt inverter battery. It has auto slice off office to quit charging when the battery achieves full charge. The charger uses a 24 volt sunlight based board as info. 

The circuit utilizes a variable voltage controller IC LM 317 to set the yield voltage enduring around 16 volts. Variable resistor VR controls the yield voltage. At the point when the sun oriented board produces current, D1 forward inclinations and Regulator IC gets data current. Its yield voltage relies on upon the setting of VR and the yield current is controlled by R1. This present goes through D2 and R3. At the point when the yield voltage is above (as set by VR) 16 volts, zener diode ZD2 directs and gives stable 15 volts for charging. 

Charging current relies on upon R1 and R3. Around 250 to 300 mA current will be accessible for charging. Green LED shows charging status. At the point when the battery accomplishes full voltage around 13 volts, Zener diode ZD1 leads and T1 forward predispositions. 

This empties the yield current out of the controller IC through T1 and charging procedure stops. At the point when the battery voltage lessens underneath 12 volts, ZD1 turns off and battery charging begins once more.

Solar Inverter Battery Charger Circuit Schematic

LM317 datasheet

Here is a vitality sparing sun oriented inverter battery charger. It gathers sunlight based vitality to recharge 12 volt inverter battery. It has auto slice off office to quit charging when the battery achieves full charge. The charger uses a 24 volt sunlight based board as info. 

The circuit utilizes a variable voltage controller IC LM 317 to set the yield voltage enduring around 16 volts. Variable resistor VR controls the yield voltage. At the point when the sun oriented board produces current, D1 forward inclinations and Regulator IC gets data current. Its yield voltage relies on upon the setting of VR and the yield current is controlled by R1. This present goes through D2 and R3. At the point when the yield voltage is above (as set by VR) 16 volts, zener diode ZD2 directs and gives stable 15 volts for charging. 

Charging current relies on upon R1 and R3. Around 250 to 300 mA current will be accessible for charging. Green LED shows charging status. At the point when the battery accomplishes full voltage around 13 volts, Zener diode ZD1 leads and T1 forward predispositions. 

This empties the yield current out of the controller IC through T1 and charging procedure stops. At the point when the battery voltage lessens underneath 12 volts, ZD1 turns off and battery charging begins once more.

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CELL PHONE EMERGENCY CHARGER

Homemade Cell Phone Emergency Charger Pack Circuit

It frequently happens, our wireless goes into a low battery condition right amidst a vital discussion, and much more dreadful it happens while we are voyaging or arranged in some remote open air area where there's no charging office accessible. Regardless, this little pack will give your mobile phone a quick refill each time it has a tendency to get level outside. 

We all realize that at 3.7 V DC, a mobile phone battery is thought to be completely charged. 

For charging it at the above level a charging source needs to give around 4 to 5 volts to the released wireless battery. 

Since here we are talking about a vitality exchange from one battery to the next or rather from some force source to the mobile phone, we have to have some kind of chargeable battery pack which would create the obliged 4 volts and which could be utilized at whatever time for charging a level PDA just by incorporating the two together. 

The above crisis battery pack can be effectively made by putting four Ni-Cd cells in arrangement. 

How about we figure out how to do it. 

It's not troublesome, you would oblige four 1.2V Ni-Cd AAA penlight cells, a four cell holder get together and a 1 Ohm 1 watt resistor.

The above holder would generate a voltage of about 4.8V at its wire terminals with four AAA 1.2 Ni-Cd attached to within the given slots correctly.

The 1 Ohm resistor can be connected at the center of the red wire by cutting the red wire at the center and bridging the resistor terminals such that it comes in series with the red wire. The resistor should covered under a plastic tubing or sleeving.

The red and the black wires of above assembly should be terminated with a suitable cell phone charger-pin so that it can be easily inserted into the cell phone charging socket whenever required.

Now let's learn how we can charge the above emergency battery pack at home.

Ni-Cd cells can be charged safely for about 10 to 14 hours using a constant voltage charger at C/10 rate. The very useful 7805 voltage regulator IC can be used here for charging the Ni-Cd battery pack.

The following diagram shows a very simple Ni-Cd charger circuit which can be used for charging the above battery pack so that it remains in a standby position and can be taken outdoors in the form of an emergency cell phone charger unit.

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6V 4AH AUTOMATIC BATTERY CHARGER

Make a 6v 4ah Automatic Battery Charger Circuit without Using a Relay

The following circuit shows a simple automatic 6 volt 4 to 10 AH battery charger circuit using a 12 volt relay.

 The following circuit shows a simple automatic 6 volt 4 AH battery charger circuit without using a relay, rather directly through a transistor.

Both the above circuits will perform equally well, however the upper circuit can be altered to handle high currents even up to 100 and 200 AH just by modifying the IC and the relay. The lower circuit may be made to do this only up to a certain limit, may be up to 30 A or so.

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FM BUG TRANSMITTERS

Spy Circuits - FM Bug Transmitters

ADC0804 (pdf) 

Easy to electronic converters find titanic application as a midway device to change over the signs from easy to cutting edge structure. These propelled signs are used for further get ready by the automated processors. Distinctive sensors like temperature, weight, power et cetera change over the physical qualities into electrical signs that are straightforward in nature. 

ADC0804 is a normally used 8-bit easy to cutting edge convertor. It is a lone channel IC, i.e., it can take one and just straightforward banner as data. The mechanized yields shift from 0 to a most compelling of 255. The step size can be adjusted by setting the reference voltage at pin9. Exactly when this pin is not joined, the default reference voltage is the working voltage, i.e., Vcc. The step size at 5V is 19.53mV (5V/255), i.e., for each 19.53mV climb in the basic data, the yield vacillates by 1 unit. To set a particular voltage level as the reference regard, this pin is joined with an expansive bit of the voltage. A valid example, to set a reference of 4V (Vref), pin9 is connected with 2V (Vref/2), thusly decreasing the step size to 15.62mV (4V/255). 

ADC0804 needs a clock to work. The time taken to change over the basic quality to modernized worth is liable to this clock source. An external time can be given at the Clock IN pin. ADC 0804 similarly has an inbuilt clock which can be used as a piece of nonappearance of external clock. A suitable RC circuit is related between the Clock IN and Clock R pins to use the inward clock.

The second illustration beneath shows another single transistor FM spy circuit that consolidates a tuned circuit or a recurrence deciding stage in it. In the first model the loop was made by scratching a winding track design on the PCB itself, however for ideal pick up and execution such carved reception apparatus curl must be stayed away from and the customary wire twisted kind of loop must be utilized.

Beneath's another circuit you would like to think about. The circuit fundamentally makes utilization of the "Q variable" of the tank system accomplished from the curl and the capacitor for producing a moderately high voltage. This ventured up potential qualities the circuit with a fairly more scope of transmission. 

For an enhanced execution verify the loop and the capacitor are situated as close as could reasonably be expected. Embed the curl leads as where it counts the PCB as could reasonably be expected so as to make it firmly embracing the PCB. C2 quality could be changed for accomplishing far and away superior reaction from the circuit. Ideally a 10pF could be attempted. The curl is made of 5 turns of 1mm thick super enameled copper wire, with 7mm width.

The next FM transmitter design is a bit different than the above types. Fundamentally the design could be classified as a common emitter type, unlike the others which are rather common base types with their design. The circuit employs an inductor at its base which adds a better saturation capability to the device which in turn allows the transistor to respond in a much healthier way.

The following configuration in the rundown is much better than its past partners since it utilizes a slug based variable inductor. This empowers the transmitter to be tuned by altering the slug center utilizing a screwdriver. In this setup we can see the curl being connected to the gatherer of the transistor which permits a gigantic 200 meters extent to the configuration, with a present that may be not more than 5mA. The MIC stage is disconnected from the base with the assistance of a 1u capacitor and the addition of the mic could be very much changed by conforming the arrangement 22k resistor. 

This circuit could be appraised as the best as far reach is concerned anyway it may need dependability which could be enhanced, we'll figure out how in the accompanying clarification.

The soundness of the above circuit could be enhanced by tapping the reception apparatus from one top turn of the curl as demonstrated in the accompanying figure. This really improves the reaction of the circuits because of two or three reasons. The radio wire gets detached from the authority of the transistor permitting it to work openly without pointless stacking, and the slipping of the recieving wire to the top further permits the applicable side of the curl to get a higher ventured up voltage prompted crosswise over itself furthermore the loop producing a higher convergance of transmission power on the reception apparatus. Despite the fact that this improvement may not real build the scope of the gadget, it verifies that the circuit does not get shook when hand held, or when the grasp is encompassed close over the circuit inside its walled in area.

On the off chance that you need your bug circuit to transmit music as opposed to spying or listening stealthily, you would likely locate the accompanying configuration fascinating. The proposed FM transmitter will permit joining a stereo data at the same time from the source so that the information contained inside both the channels get into the air for an ideal gathering. The outline arrangement is truly indistinguishable to the particular case that's talked about above so does not require quite a bit of a clarification.

Breaking down a Two Transistor Spy Circuit 

Adding a transistor stage to the above talked about single transistor FM transmitters could empower the outlines with amazing affectability. An electret MiC itself has an implicit FET which makes it exceptionally productive and makes it a stand alone vibration speaker gadget. Including another transistor stage with it upgrades the affectability of the gadget as far as possible. As may be seen in the accompanying chart, the association of an additional transistor stage signifies the increase of the MIC making the whole unit very delicate such that it now picks even the sound as low as a pin dropping on the floor . The additional transistor averts over the top stacking of the MIC along these lines guaranteeing better proficiency to the affectability.

Five things that that make the circuit greatly great with it gathering are: 

The utilization of a fix capacitor in the tank circuit alongside a movable trimmer. 

A low esteem coupling capacitor with the MIC adequate to handle the capacitive reactance of the MIC which may be around 4k at 3kHz. 

A 1u coupler is incorporated between the oscillator and the sound enhancer keeping in mind the end goal to compensate for the low impedance rendered by the 47k base resistor. 

The loop utilized is twisted for all intents and purposes utilizing super enameled copper wire which guarantees higher effectiveness than PCB scratched sort of curl. 

The whole circuit could be minimally developed more than a little estimated PCB for procuring better solidness and a float free recurrence reaction.

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INDUCTANCE METER

Inductance Meter Circuit

The article discusses a simple yet accurate, wide range inductance meter circuit. The design utilizes only transistors as the main active components and a handful of inexpensive passive components.

The proposed Inductance meter circuit can measure inductance or coil values accurately over the given ranges and as a bonus the circuit is also capable of measuring the complimentary capacitor values as accurately.

The circuit functioning may be understood with the following points:

As we all know that inductors are fundamentally related to generating frequencies or in other words with pulsating or AC supplies.

Therefore for measuring such components we need to force them with their specific functions in order to enable extraction of their hidden characteristics or attributes.

Here the coil in question is forced to oscillate at a given frequency, and since this frequency depends on the L value of the particular inductor becomes measurable through an analogue device such as a moving coil meter after suitably converting the frequency into amplified voltage/current.

In the shown inductance meter circuit, T1 along Lo, Lx, Co, Cx together forms a Colpitts oscillator type of self oscillating configuration, whose frequency is directly determined by the above L and C components.

Transistor T2 and the associated parts help amplifying the generated pulses at the collector of T1 to reasonable potentials which is fed to the next stage comprising T4/T5 for further processing.

The T4/T5 stage raise the current and integrate the acquired info to appreciable levels so that it becomes readable over the connected uA meter.

Here Cx and Co basically provides the range selection option, many good quality caps with precise values may be positioned in the slot, with a provision of selecting the desired one via a rotary switch. This will allow an instant selecting facility of any desired range for enabling wider measurement of any particular inductor.

Conversely, correctly measured inductors/capacitor may be positioned at Co, Lo and Lx for getting an equivalent meter deflections for any unknown capacitor at Cx.

P1 and P2 may be used for monitoring and adjusting the zero position of the meter, it also allows fine tuning of the selected range over the meter.

Meter FSD calibration can be achieved by using the formula: ni = nm(1 – fr)/(1 – fc) where ni is the number of divisions measured on the scale, nm = total number of division of the scale, fr = relative frequency, fc = the smallest relative frequency measured.

The current consumption would be around 12mA at 12V while an inductor is being measured.

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