The question was, "How do I find cheap freelance hardware and software developers?"
I warned the questioner to be very careful about what he was asking for:
First of all, you don’t want “cheap” developers; you want inexpensive developers.
Second, the expense of developers is not their hourly or daily rate. It’s the total cost of building and delivering the software and hardware you want.
In my experience, the least expensive developers have much higher rates than the more costly ones. The deliver what you want, the first time, in less time, with less trouble.
However, a high hourly rate doesn’t guarantee an inexpensive product. Freelance developers can charge anything they want, so price doesn’t necessarily indicate value.
Instead, speak to references about any developer you’re considering. Find out first hand what you’re going to get for what you’re paying.
And, by the way, don't think you'll save money by hiring individual developers. Your best bet will generally be to choose a team, perhaps an Agile team, but in any case, a team that has a history of working well together.