This battery horse route differs from the normal in a number of ways, all of that make it tough to understand. For this reason, we do not suggest it is to beginner.
Repairing /revamping a deceased horse
What we proposed with was an potential 12amp battery charger. In hope of repair it, we traced out the circuit, but did not similar to what we found"poor route design. So what we had to beginning with was an enclosure, ammeter, thermal bog down interrupter, and center-tapped transformer all written for battery horse application.
Since the limit stream delivered by the section is a function of the transformer inner impedance, we suggest that the readers use the same sort of transformer. If you are a great pack-rat (like me), you may already have a deceased charger"or you may be on the surveillance for one.
SCR (Thyristor) Rectifiers
First of all, the two SCRs (silicon tranquil rectifiers or thyristors) are related with their anodes (stud or tab) grounded"this creates for glorious thermal give since no insulating hardware is compulsory (if it is slight to link up the disastrous depot of the horse right away to the steel enclosure). If you do not instruct to belligerent this point, use insulating hardware to electrically keep apart from the SCRs. This creates the transformer center-tap the certain terminal. The reason for this route chain is the ease of pushing the SCR gates around the certain battery voltage"it is really unorthodox as we have never seen this pretence completed before.
SCRs are the preferred power device selection for a battery horse since they can both systematize battery charging voltage and head off mistake stream when the battery is inadvertently related reverse. we have obviously related cave retreat and think that the horse was potential until we satisfied what we had done.
Power Device Selection
I used two 2N690 stud-mount SCRs that we had available. Any in the array will work (2N683 by 2N690)"only the voltage rating differs and anything larger than 100V is great is to application. Other more cheap TO-220 possibilities are: STMicroelectronics TYN616, Teccor/Littlefuse S6015L (isolated package), NXP 151-500C, or ON Seimconductor 2N6403G. Avoid sensitive embankment devices.
Circuit Common
Normally circuits use a disastrous common"that is only the way the world seems to work, but in this case, it was more available to make the certain rail the familiar indicate and all cognisance contingency be made with this in mind. The only difference is D7 that was commissioned to head off damage should the battery obtain related reverse. For visualization, simply partial out D7. The established belligerent pitch is used is to disastrous rail. This tends to tie your brain in knots...
Voltage Reference
A great battery horse tapers off when the battery voltage is on top of about 14V. For this to function, D6 is a 5.1V shunt zener regulator that puts out -5.1V relations to the certain rail. It is inequitable around R8.
Ramp Generator
C1 and R4 form a ramp generator of electric power that generates a disastrous going sawtooth voltage (relative to the certain rail). It is reset to the certain rail around Q1 and Q2 at line voltage 0 crossing. At 0 crossing, there is no voltage at the anodes of D3 D4 (relative to the certain rail), Q1 is off, Q2 is on and C1 is shorted. At all other points in the AC line cycle, C1 is charging. My line magnitude is 60HZ. For 50HZ, enlarge the worth of R4 to 82K.
Error Amplifier
U1A is the blunder amplifier"it amplifies the difference between the -5.1V anxiety voltage and the feedback voltage at the arm of the V ADJ pot (R6). It is slowed down by the RC filter (R10 C2), proportionately amplified by the proportion of R14 /R9, and integrated around C3. Perhaps you have listened of a PID (proportional, integral, derivative) control"this does only that, but neglects the derivative tenure as it is normally not compulsory in many applications. If the blunder amplifier is not satisfied, it continues to confederate its outlay voltage until the feedback voltage equals the anxiety voltage. The function of the functional amplifier is to make the two submit voltages equal.
The device selection here is the LF442 (or TL082) J-FET submit functional amplifier. This is key in this route since the familiar mode voltage operation of the differential inputs contingency expand to the certain rail. Few op amps can do this (many have differential voltages that expand to the disastrous rail, but those will not work in this application).
Phase Comparator
U1B is the state comparator. It compares the ramp voltage with the outlay of the blunder amplifier. It is moreover called the ramp-intercept technique. When the ramp generator of electric power voltage exceeds the blunder voltage vigilance (in the disastrous direction), the outlay of U1B switches disastrous and turns on Q3 thus providing embankment stream to the SCR that is deliver biased. R13 is the embankment stream tying resistor.
Flashing a Dead Battery
The battery provides the power to begin operation of the regulator circuit, so if the battery is entirely liberated it may be necessary to "flash" the battery terminals with a great battery to bootstrap the regulator in to operation.
I have toyed with the idea of installing a "Flash" pushbutton, but this adds more electronics and we have not found it necessary.
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