Driver Chips and solutions - ULN2308 versus 74LS07 [or 74LS06]
LoopyByteloose
Posts: 12,537
Everyone seems to turn to the ULN2308 as a driver for several reasons. One is that it has 8 lines in parallel. Another is that it allows one to shift from +5volts to higher voltage output.
If one doesn't need 8 lines, the hex 74Ls07 buffer/driver is another good choice. The biggest draw back is that the i/o layout is not parallel. Each is paired and next to each other. But it will handle switching voltages up to 30volts and power up to 40ma.
Of course, if you really need power, the 2N2222 remains even more useful. But, I really want to focus on the IC packaged devices.
I personally feel the 74LS07 is a great protector of output pins and a good driver for LEDs, especially the newer, brighter ones. It can also easily adapt to driving relays and small motors . And with the 74LS06, one can invert logic so that states of output cannot possibly conflict. So I wonder why it is often ignored?
I suspect a lot of us overlook the meaning of 'open collector' when we are selecting chips.
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It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).
Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
If one doesn't need 8 lines, the hex 74Ls07 buffer/driver is another good choice. The biggest draw back is that the i/o layout is not parallel. Each is paired and next to each other. But it will handle switching voltages up to 30volts and power up to 40ma.
Of course, if you really need power, the 2N2222 remains even more useful. But, I really want to focus on the IC packaged devices.
I personally feel the 74LS07 is a great protector of output pins and a good driver for LEDs, especially the newer, brighter ones. It can also easily adapt to driving relays and small motors . And with the 74LS06, one can invert logic so that states of output cannot possibly conflict. So I wonder why it is often ignored?
I suspect a lot of us overlook the meaning of 'open collector' when we are selecting chips.
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It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).
Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
Comments
Jameco····· 76c-$1.03·· 74c-$1.09· ·64c-$1.05
Digikey····$1.05-1.35·· ·· 90c····· ·· 90c
If you have 'em, then use 'em.· If you're buying from Jameco, there's no price difference.· The 2803s are set up with the free-wheeling diodes for each gate.
Either way, if you burn a gate you lose the whole package.
Transistors cost least (but they aren't in a DIP.)
PJ's right... if you have them use them... If you can live with about a 36% current hit and two less pins, then use the 74LS06 or the 74LS07.
·
The ULN2803 is an Octal driver capable of handling a total current of 500mA (62.5mA per pin)
The 74LS06 is a hex inverter capable of handling 40mA of current per pin (240mA total current)
The 74LS07 is a hex buffer capable of handling 40mA of current per pin (240mA total current)
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 7/27/2008 8:47:44 PM GMT
On the one hand, I really thought the ULN2308 was always more expensive due to added features. It seemed a bit of overkill to drive multiple LEDs while protecting a BasicStamp's I/O from overload.
On the other, the ULN2308 is the easiest to wire up as the pin arrangement is quite clean.
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It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).
Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
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Chris Savage
Parallax Tech Support
{Chris's correction}
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It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).
Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
Post Edited (Kramer) : 8/1/2008 5:59:32 PM GMT
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Chris Savage
Parallax Tech Support
In concept, the point is that there are other driver ICs that offer interesting choices including latches and buffers that can be bidirectional.
I am just try to figure out which contexts are useful to either protect the BasicStamp or to eliminate some of the more mundane work load. We mostly seem to expect the BasicStamp to do everything. Some of these 'glue chips' can free the BasicStamp to do more powerful things [noparse][[/noparse]like monitor sensors rather than generate PWM for motors].
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It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).
Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan