Oakley MOTM-820, OMS-820 manual

voltage across the capacitor will directly control the output of the MOTM module. When the OMS-820 is connected up it will supply the input voltage to the MOTM and thus the maximum level applied to that capacitor. It also needs to keep an eye on the output voltage too.

As with many electronic circuits the OMS-820 can be split up in several little chunks. Grab hold of the schematic now and let’s run through each bit in turn.

The LFO section is that bit centred around dual op-amp U1. This bizarre looking circuit is actually called a precision Schmitt Trigger. The input comes in to the BUFFERED node. The voltage at this point is a copy of the output of the MOTM module. U1 (pins 1,2,3) acts as a comparator. When the voltage on pin 3 is more positive than the voltage on pin 2, the output at pin 1 swings highly positive (high). When the voltage at pin 3 is more negative than the voltage on pin 2, the output goes highly negative (low). Now because pin 2 is connected to zero volts, or local ground, any positive voltage at pin 3 will make pin go high.

The output of the op-amp drives a transistor output stage. This set of four transistors simply act as a switch that will give either +15V or -15V depending on the polarity of the output of the op-amp. Op-amp outputs can’t, in general, actually go right to their supply rails. So the high state is more likely to be +13V or so, while the low state is probably -13V or so. To make a good symmetrical LFO waveform we really should have a accurate swing from plus to minus. ‘Probably’ +13V is not good enough. I want exactly 15.00V... well, not exactly, but the closer the better. So simply put, those four transistors provide a near perfect symmetrical output swing from an imperfect op-amp output.

The U1 (pins 5,6,7) op-amp performs two important jobs. Firstly it steps down the +/-15V swings to a more reasonable +/-7.5 volts. This gives us the peak charging voltage for the MOTM-820’s input. This is not very important for when the MOTM-820 operates in the linear mode, but it sets the asymptote of the log curves in the LOG mode. Leaving this at +/- 15V would give an unsatisfactory log response, making the LIN/LOG pot do very little. The second function of the op-amp is to invert the output. Inversion is all important to get the thing to oscillate, more about this later.

Let’s go back to the first op-amp again, and have a look at pin 3. Pin 3 gets its instructions from two sources. Firstly the voltage on the BUFFERED node, ie. the output voltage of the MOTM-820. Secondly, the highly symmetrical output of the transistor switcher. The ratio of R12 to R13 sets the weighting each input has on the final output. It is this weighting that is crucial to the operation of the LFO mode. Say the output of the switcher is at -15V, then with zero volts at the BUFFERED node, the switcher’s output will stay stuck at -15V. Its staying in the low state by its own output forcing pin 3 low. However, consider what happens as the voltage on the BUFFERED node starts to rise, so does the voltage on pin 3. At around +5V, the voltage at pin 3 is approaching zero. As the voltage rises and crosses zero, the op-amp flips state to its high level. The switcher responds and flies to +15V. This is fed back into pin 3 via R13 and forces it higher still. The op-amp is now stuck in a high state.

But remember that the BUFFERED node is being driven by the MOTM module, which in turn is being driven by the output of the inverting amplifier, U1 (pins 5,6,7). This output is now negative, so the MOTM-820 now forced to discharge, and hence its own output will fall. The falling voltage now causes pin 3 to slowly fall from a positive value back to zero. And once

MOTM-820, OMS-820 specifications

The Oakley OMS-820 and MOTM-820 stand out as exemplary models in Oakley's extensive range of performance eyewear, designed for both sports enthusiasts and everyday users. These models capture the essence of Oakley's commitment to innovation, superior optical technology, and stylish design.

One of the main features of the OMS-820 is its advanced lens technology. Utilizing Oakley’s High Definition Optics (HDO), the lenses provide exceptional clarity and optical fidelity. This technology minimizes distortion, ensuring that users have an unobstructed view, whether they are on the golf course, cycling, or participating in other outdoor activities. The lenses also come with Oakley's PRIZM technology, which enhances color contrast and visibility in various environments, allowing users to detect changes in terrain or obstacles more readily.

The MOTM-820, on the other hand, emphasizes adaptability and comfort. It features a lightweight frame crafted from Oakley’s proprietary O Matter material, which provides flexibility and resilience. This ergonomic design conforms to the shape of the wearer's face, ensuring a secure yet comfortable fit during extended use. The adjustable nose pads and temples further enhance comfort, making it ideal for an active lifestyle.

Both models incorporate Oakley’s innovative lens treatment technology, which includes anti-fog and anti-scratch advancements. This ensures that the eyewear remains clear in challenging conditions, whether users are facing misty weather or rugged terrains. Additionally, the UV protection offered by these lenses shields wearers from harmful rays, a critical feature for outdoor activities.

A striking characteristic of the Oakley OMS-820 and MOTM-820 is their customizable aesthetics. Available in a myriad of colors and styles, users can express their individuality while enjoying high-performance eyewear. This attention to style combined with functionality makes these models popular choices among both athletes and casual wearers alike.

In summary, the Oakley OMS-820 and MOTM-820 are distinguished models that integrate cutting-edge technology with comfort and style. Whether for competitive sports or daily wear, these eyewear options exemplify Oakley’s commitment to enhancing visual performance and user satisfaction.