Available online
Description
The programme looks at various pneumatic circuits used for control purposes, discussing positive and negative feedback etc.
The programme looks at various pneumatic circuits used for control purposes, discussing positive and negative feedback etc.
| Module code and title: | PET271, Technology for teachers |
|---|---|
| Item code: | PET271; 05 |
| First transmission date: | 22-05-1975 |
| Published: | 1975 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:24:31 |
| + Show more... | |
| Producer: | Tony Jolly |
| Contributors: | John Sparkes; John Whatley |
| Publisher: | BBC Open University |
| Keyword(s): | Animated diagrams; Lever window; Model steam engine; Postive and negative feedback; Single/double acting valves |
| Footage description: | Whatley operates a pneumatically controlled hack saw machine. He moves to a board a with single acting cylinder and circuit diagram to show how it works. He operates the circuit and uses an animated diagram as explanation. Sparkes explains a circuit diagram to control opening and shutting of a louvre window. He explains on a diagram how he could arrange a circuit to stop the window in varying positions. Whatley demonstrates a model to show Sparkes' diagrams in practice. The pneumatic system judders. He examines a new circuit, which involves 3 and 5 port valves and a double-acting cylinder. He explains the circuit diagram. Returning to the actual model, Whatley repeats the demonstration showing how judder can be eliminated by moving one valve. Whatley returns to the hack saw machine, describing how the circuit is controlled in the way outlined above. Shots of machine working. Sparkes operates a cut away model of a steam engine. He explains in detail how the engine operates - valves, pistons etc - when steam enters the mechanism. He explains what is meant by negative feedback and discusses the function of the governor in a steam engine. Using close-ups of an ordinary mains electric switch, Sparkes explains what is meant by positive feedback. Whatley reinforces the concept of positive feedback with a lever system linked to a pneumatic circuit. He briefly introduces the concept of hysteresis. Credits over model of steam engine. |
| Master spool number: | 6HT/71610 |
| Production number: | 00525_6087 |
| Videofinder number: | 655 |
| Available to public: | no |
