When you sit down to write an essay on technology, ask yourself: is this a technical paper, or a social paper?
Depending on whether you're going to focus on the intricacies of the underlying tech or the ramifications it has on the human condition, you'll have a very different set of essay topics on technology to choose from.
If you're writing a technical paper, the topic needs to be something that you can understand well. Such a paper needs to show that you have a thorough comprehension of what's going on, be it software or hardware. You should be able to show that you can not only explain the function and application of a technical concept, but that you can predict how it will interact with other elements of a larger system when you bring it to bear on a problem. When you understand a topic thoroughly, you can explain what may a very complex implementation in a few well-chosen words. This kind of explanation is what wins you big points on an essay on technology.
To write a good essay on technology one needs to have enough knowledge
On the other hand, socio-technical papers loose out if they delve too deep into the technical underpinnings of phenomena. Even if you have an incredible understanding of how it works, the best way to convey this is not to try at all: instead, let your knowledge inform the broader statements you make, keeping you from making the minor mistakes.
If you've chosen a socially oriented one from the many possible essay topics on technology, spend your efforts thinking about what the implications of a technology are for the people who have to use it, or the people whose lives it touches. Who does it help, and why? Does it disadvantage some people as it helps others?
The trick with a technology essay is moderation and restraint. Just about any system is too complex, and its social implications too far-reaching, to fully encapsulate in the space of an essay. Your task as the writer is to pick a particular window that, in peering through, will let your reader understand the whole from a view of the part.