Jim's FAQ's

Are the contacts included with the D38999 series 3 connectors, or ordered separately?

messages@element14.com — Tue, 16 Mar 2010 15:24:57 GMT

Contacts are normally included with the D38999 D38999 series of connectors, however a number of exceptions do exist. One of them is when the part number used to order the connector has an “-LC” suffix at the end. Another exception is how the part number is assembled. Normally at the end of the part number there’s a “P” or ‘S” to denote the gender of the contacts used in the connector (“P” for pins, “S” for sockets). If these are switch to an “A” or “B”, then the contacts are again omitted and must be purchased separately. Some example part numbers are shown below.

These 2 part numbers include contacts.

D38999/20JE26PN

D38999/20JE26SN

While the 3 below do not include the contacts

D38999/20JE26PN-LC

D38999/20JE26AN

D38999/20JE26BN

Please review the manufacture’s documentation for full ordering details as well as options for specific applications.

What’s the difference between “diffuse reflective” and “retro reflective” photoelectric sensors?

messages@element14.com — Mon, 08 Mar 2010 18:16:13 GMT

Photoelectric sensors consist of an emitter and receiver, the emitter sends out a beam of light for the receiver to sense. With the diffused and retro reflective type of sensors both the emitter and receiver are placed in the same housing and are configured for light to be reflected back to the sensor.

Retro reflective sensors use a target to reflect light back to the sensor and will sense an object that breaks the beam’s path. The diffuse reflective type senses an object when the light beam is reflected back to the sensor. Additional features as well as different form factors will vary from series to series.

Isn’t Watts (W) and VoltAmps (VA) the same?

messages@element14.com — Tue, 26 Jan 2010 19:14:13 GMT

The “Volt-Ampere” is the measure of “apparent power” and is used primarily in circuits using alternating current (AC). The Volt Ampere (VA) consists of 2 components, the first is the real power known as Watts, while the other is the reactive power known as VAR (Volt-Amps-Reactive). The following equation shows how the 3 terms are related: VA = (W² + VAR²)^1/2. In DC circuits, the VAR term drops to 0 since reactive power doesn’t show up in DC. More information on this topic can be found here

A common graphical representation of the relationship between these three components is the power triangle. The real power (Watts) makes up the adjcent leg, reactive power (VAR) makes up the opposite leg, and the apparent power (VA) is the resulting hypotenuse.

Do variances in an op-amp’s supply voltage affect the output?

messages@element14.com — Mon, 18 Jan 2010 15:52:41 GMT

While op-amps are designed to reject noise and other disturbances in the supply rails, shifts in the supply voltage can affect the output of the op-amp. Just how much the op-amp may be affected depends on a number of factors (noise, frequency, temperature, degree of change in voltage, etc). The op-amp’s power supply rejection ratio (or PSRR) can give a good estimation of how much an output can be affected by noise or changes in the supply rail. The PSRR is frequency dependant so its value will change under different circumstances. The voltage delivered to the op-amp’s supply pins should be kept constant, within the manufacture’s specifications, and as noise free as possible.

For Op-Amps, does the supply voltage need to stay at the maximum voltage listed?

messages@element14.com — Mon, 11 Jan 2010 20:19:52 GMT

Many op-amps can work off of a range of voltages; however, some characteristics of the op-amp may behave differently at different supply voltages. Check the manufacture’s datasheet for details on the working specifications for the device at the voltage you want to run it at. The supply voltage should not exceed the specifications given by the manufacture and should remain constant. Special considerations may apply to particularly low voltage levels.

Is it important for a coax connector’s impedance to match the impedance of my cable?

messages@element14.com — Mon, 04 Jan 2010 14:40:18 GMT

Having a coax connector that doesn’t match a coaxial cable’s characteristic impedance can lead to reflections, attenuation, and other signal problems. Since many coaxial connectors come in 50 & 75 ohm versions, many manufactures list the RG cable rating individual connectors are compatible with. Matching the RG cable rating will ensure that not only will the impedance match but the connector’s physical size will match the cable as well.

Can I assume that a “Rail to Rail” Op-Amp will have this feature on both the input and output?

messages@element14.com — Mon, 28 Dec 2009 14:15:11 GMT

Not necessarily! Op-Amps can have the “Rail to Rail” feature on the input only, output only, or both. Different circuit parameters can also affect just how close to the rail the Op-Amp can go (for example, the load current can limit the output voltage of an op-amp with rail to rail output). Be sure to check the manufacture’s datasheet to ensure its configuration will match your requirements.

What size backshell will fit by Combination D-Sub connector?

messages@element14.com — Tue, 17 Nov 2009 16:16:12 GMT

Combination (or Hybrid) D-Subminiature connectors are made to standard d-sub sizes. For the most part, standard d-sub backshells will fit a Combo-D. ITT Cannon and Amphenol both have tables in their catalogs that give the shell sizes for the more popular layouts. The table below is a condensed version. For full details please refer to the connector manufacture's documentation. Approximate equivelant collumn refrences standard size d-sub connectors (not high density types). Links to ITT's and Amphenol's D-Sub catalogs are below.

	D-Sub Shell size code		Approximate
Arangment	ITT code	Amphenol code	Equivelant
2W2	DE		9 Pin
5W1	DE	E	9 Pin
3W3	DA	A	15 Pin
7W2	DA	A	15 Pin
11W1	DA	A	15 Pin
5W5	DB	B	25 Pin
9W4	DB	B	25 Pin
13W3	DB	B	25 Pin
17W2	DB	B	25 Pin
21W1	DB	B	25 Pin
8W8	DC	C	37 Pin
13W6	DC	C	37 Pin
17W5	DC	C	37 Pin
21W4	DC	C	37 Pin
25W3	DC	C	37 Pin
27W2	DC	C	37 Pin
24W7	DD	D	50 Pin
36W4	DD	D	50 Pin
43W2	DD	D	50 Pin
47W1	DD		50 Pin

ITT Cannon: Combo D section , D-SUB Full Line (4.3Mb and 9.75Mb respectively)

Amphenol: D-Sub full catalog (40Mb download)

What are NPN and PNP outputs on sensors?

messages@element14.com — Mon, 02 Nov 2009 15:30:46 GMT

The outputs of some sensors will behave like transistors, when a sensor senses an object it will trigger the transistor controlling the output (which essentially acts like a switch) and depending on its design it’ll act as an NPN or PNP type transistor. An NPN output is commonly called a “sinking” output. When the sensor senses an object it will connect the output to the negative supply. A PNP output is commonly called a “sourcing” output. When it senses an object it will connect the output to the positive supply. If you’re unsure of which output type you need, a number of manufactures produce sensors with configurable outputs. In this case the sensor can be configured to operate as an NPN or PNP type. NPN, PNP, and Configurable type sensors come in a Normally Closed and Normally Open configurations.

What is the difference between inductive and capacitive sensors?

messages@element14.com — Mon, 12 Oct 2009 19:26:48 GMT

Inductive sensors use a magnetic field to detect objects. Capacitive sensors use an electric field. In order to be sensed by an inductive sensor an object must be conductive. This limits suitable targets to metal objects (for the most part). In order to be sensed by a capacitive sensor the target doesn’t need to be conductive. A capacitive sensor will react to an object acting as a dielectric material as well as a conductive object. This makes metal and non-metal objects suitable targets.

What’s the difference between Multicomp’s Vapo Bearing fans and a normal sleeve bearing fan?

messages@element14.com — Thu, 08 Oct 2009 19:23:41 GMT

The fans from the Multicomp brand that feature the “Vapo Bearing” have an extra magnet in the motor and shaft area. This extra magnet helps to stabilize the rotating fan reducing friction between the shaft and the bearing. In this increases the life of the fan while reducing motor noise.

What is a “Peltier”?

messages@element14.com — Tue, 29 Sep 2009 14:01:43 GMT

A “Peltier” is a solid state Thermoelectric Module. When powered, it acts like a solid state heat pump (thanks to the Peltier effect) that transfers heat from one side of the device to the other. Computer enthusiasts sometimes place the wafer like device on top of the processor of their computer with the hot side facing a water block to enhance the cooling of the processor. Thermoelectric Modules ratings include max temperature difference and max cooling capacity, among others.