Pulse generator for gas injectors that you can do at home. Simple to assemble and without many components. Made by Mechanical Girl.
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Hello, dear readers, in view of the large number of questions with my other tester of injectors, referring to that if you could achieve the modulation of the frequency of activation of the injector ... well in that is not possible, but in this article if I bring you one that does. As always, easy to assemble and implement. Without further ado, in the following figure I show you the electrical circuit, with few materials.
U2: Regulador de voltaje 9V LM7809
C1: condensador electrolítico 1uF 16V.
C2: condensador electrolítico de 400uF 16V
R1, R2: Resistor de 10k ohms.
RV1: Potenciómetro de 250k ohms.
D4, D5, D3: Diodo rectificador 1N4007.
C5, C3: Condensador electrolítico de 10uF 16V.
R11, R10, R4: Resistores de 1k ohms.
C4: Condensador de 22uF 16V.
RV2: Potenciómetro de 20k ohms (opcional).
Q1: Transistor bipolar NPN TIP 122.
D2: LED Verde.
D1: LED Rojo.
R3, R5: Resistor de 680 ohms.
On the internet there are many circuits, but after reading and assembling many, most have technical details to correct, they are usually values of bad resistances that in my opinion is purposely not to make it so easy for copiers. LOL. Others have too many components, in short, those circuits served as inspiration to mount this pulse generator.
As you can see, it is based on the popular timer circuit LM 555, adjusted to produce pulses of about 3hz at 30hz, using the RV1 potentiometer, and injection openings of 20ms to about 40ms (turn off the pulse) with RV2. RV2 is optional, you can replace it with a cable and for that case, the injector will always open for 20ms fixed to all the power that the transistor gives.
I placed RV2 more than anything to vary the workflow of the injector, so that work colder and with less stress, the modulation of the put a little beyond the 20ms is only gain for my design. Hahaha.
The circuit is divided into three zones that fulfill a specific function that I describe below:
Injector pulse generator circuit explanation
Zone 1 - Oscillator: Basically it is a 555 configured to produce a stable square wave and that is adjustable by potentiometer RV1. The assembly of this configuration is very well explained on the internet.
Zone 2 - Trigger: this part of the circuit is responsible for giving a 20ms trigger for opening the injector, no matter how long the pulse sent by the oscillator lasts. This I did in this way, to avoid that at low frequencies of oscillation, the injector lasts too long, that the only thing it does is to heat it excessively, and it is not what we do not want.
Its operation is quite simple: Upon receiving the positive pulse of the oscillator, the C5 starts the charging process, rapidly circulating current to C4 to charge it through D4. Once charged, C5, cuts the pulse of the oscillator. At this moment the base of Q1 is polarized, producing the activation of the injector and consuming the charge of C4 through RV2 and R4.
Once the oscillator wave goes from high to low state, R11 and R10 quickly discharge to C5. And the D5 unloads capacitor C4 if it still has charge. D5, is to stabilize the injection pulse at high frequency, because without it, the injector would remain lit with pulses less than 20ms.
Zone 3 - Power: It's quite simple. RV2 and R4, are responsible for reducing the discharge time of the C4 and in turn control the current passing through the injector. It can be adjusted to the naked eye simply by seeing the degree of powering of Led D2. D1, this is to acknowledge the turning on of the transistor. So, if we have a short circuit in the Injector, D2 will not turn on and D1 will light poorly.
The activation of the injector is in charge of a TIP 122, which gives us great power to the output, but as it is bipolar generates a lot of heat, so it is advisable to place a heat sink to avoid burning it.
For this reason also place the potentiometer RV2, in order to regulate the working current of the injector so that it works smoothly and without stress.
Finally, the 9V regulator is to keep the voltage stable for the oscillator. So that when connecting or disconnecting the load of the injector, the frequency is always stable.
Although it is possible to work about 2 or 3 injection pulses at a very low frequency, it is not advisable to place an injector under cleaning at this speed. So, if you are going to use it as a cleaner, work it at a good speed, more than 10 pulses per second.
The circuit can handle if we use a good heat sink, up to 4 simultaneous injectors, but the function of the diagnostic LEDs is lost.
It is possible to add more power stages to increase the number of injectors. You just have to raise the associated resistance R4 to better distribute the discharge current of C4. Later in the next revision I place the improvement hehehehe:).
If someone has an improvement to my circuit, send it to me or let me know that I gladly review it. You just have to leave it down in the question box of this article.
Simple injectors tester: Go to article
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